Moisture sensing autodry* involves a simple pair of metal strips (electrodes), not a high-tech humidity measurement gizmo. Damp fabric brushing across the strips completes a low-voltage electric circuit. The moisture "hits" are monitored by the control board algorithms to determine when the load has reached the selected dryness level. Or, a mechanical timer is repeatedly stalled/run/stalled/run per the moisture hits on machines not equipped with electronic controls. Build-up of waxy softener residue effectively insulates the strips from registering moisture hits. Cleaning them is the fix. Replacing them is far beyond necessary. I vaguely recall mention somewhere that Miele or Bosch or some European brands had/have designs that use the drum surface as one side of the sensor circuit.

*Thermostatic autodry works by inferring dryness according to how frequently the heating element (or gas burner) is engaged. The timer stalls when the heat is on, runs when the heat cycles off at the target temperature. Evaporating moisture holds the air temperature down so the heat runs longer/more often, shorter periods and less often (so the timer runs more) as the load progresses to dryness.

I'm one of those who never uses softener or dryer sheets - no need for that stuff. Years ago I used dryer sheets to reduce static during dry MInnesotat winters, They left spots on my clothes. Haven't used them since except to keep mice out of the vehicles I put in storage over the winter.

Looks like this could be a solution

You can also make your own dupe of those products

From CR:

• Why Fabric Softener Is Bad for Your Laundry—and What to Use Instead
• 5 Things Our Laundry Expert Would Never Do

I do not use fabric softner in my washer nor do i use liquid detergent. I use powder detergent. I use dryer sheets in the dryer but not with towels or micofiber cloths. I do not use sensor dry on my dryer. Always timed dried. I hate sensor dry. The clothing is never completely dry. I wash my lint filter every so often.

Clyde Kalvin: "I do not use sensor dry on my dryer. Always timed dried. I hate sensor dry. The clothing is never completely dry."

Some dryers apparently are designed or programmed better than others for sensor dry. Mine performs fully dry at the normal dryness level, including for sheets and quilts, except one set of towels (which are decorative, so washed infrequently) that are a type of synthetic/blend fabric that the sensor bars don''t "read" accurately.

I use a light dose of liquid softener on sheets/bedding for a bit of (lavender) fragrance.

I’ve seen the same issue discussed with both washers and dryers. Fabric softener and dryer sheets can leave a film over time, but the moisture-sensor point is particularly interesting because the sensor strips need good contact with damp clothing to detect moisture accurately.

For the dryer, regularly cleaning the sensor strips with a suitable cleaner and keeping the lint filter and airflow path clean seems more practical than replacing the sensors as routine maintenance. If a dryer starts running longer than normal or clothes are coming out unevenly dry, residue on the sensor strips is one thing worth checking before assuming the sensor itself has failed.

For washers, periodic tub-clean cycles can help with buildup, but the dispenser, seals, and areas where softener accumulates also deserve attention.

I just bought a new washer and dryer and was surprised to see I no longer have any issue with static on the first few loads of laundry despite not using any fabric softener or dryer sheets.
My old dryer must have been over drying when set on sensor dry.

I add white vinegar to EVERY WASH in the fabric softner dispenser. It eliminates any odors and residual soap in my wash load.

Then I use one dryer sheet purchased from the Dollar Store along with 2 white dryer tennis balls in my dryer. This is what works for me.

I use white vinegar in both the bleach and softener dispensers in the washing machine. Nothing extra in the dryer needed, provided clothes are removed when done.

I've discovered the white vinegar trick for the rinse for towels. Helps with odor elimination.

No fabric softener or dryer sheets for me. I've never used fabric softener. I used to use unscented dryer sheets, but Miele heat pump dryer instructions say never to use dryer sheets so when I got the Miele I ditched the sheets. No need for them -- I don't get static at all with the Miele dryer.

Using fabric softener and dryer sheets occasionally is generally fine, but both can leave residue over time. Regular maintenance helps, though it may not remove all the buildup.

Run the washer's tub-clean cycle as recommended by the manufacturer, and periodically wash the dryer lint filter with mild soap and water, making sure it's completely dry before reinstalling it. Clean the moisture sensors with a soft cloth and follow the manufacturer's instructions.

If you want to avoid buildup altogether, consider skipping fabric softener and dryer sheets and using wool dryer balls instead.

@jaxo, I disassembled a couple dryers recently for clean-up and a bit of repair and have an observation on dryer sheets. Both the same brand/model (Fisher & Paykel topload dryer). One I bought new in 2004, had been used by my mother (machine A) for several years until my sister moved in w/mom and brought her machines. The other (machine B) I bought used in 2018 (it was disassembled and cleaned up at that time) and have been using it since loaning the other to mom.

The observation is that machine B was/is impressively clean. Zero lint/residue on the blower wheel and exhaust path. A bit of lint accumulation, as expected, in the filter area, but easily cleared.

Machine A had a sticky residue throughout the airflow path and notably more lint accumulation, that called for complete disassembly and washing all the parts.

Mom uses dryer sheets.

I don't.

Great question, and the fact that you already have a cleaning routine puts you ahead of most people! The buildup concern is real: liquid softener leaves a waxy coating that can clog the dispenser drawer and coat the dryer's moisture sensor bars, which is exactly why loads start taking longer to dry over time.

A couple of things that have worked well in my experience: run the tub clean cycle with hot water monthly rather than waiting for the reminder light, and wipe the dryer's sensor bars (the two metal strips inside the drum) with a little rubbing alcohol every few months — that one trick fixed my dryer running forever on sensor dry. If you like the softness, try halving the softener dose or swapping it for plain white vinegar in the rinse cycle; you still get soft towels without the gunk. With your maintenance habits, those machines should stay happy for years!

I wonder if municipal water is not as well treated as it was years ago. I never had a problem with my linens smelling sour until I bought my first new set of appliances in this new century. I do recall my Kenmore Top loader from 1987 occasionally having an odor which I attribute to the use of fabric softener when I reflect on it. That machine stayed in use until around 2005 (I was friends with the woman who bought that house from me in 1996). Never did I deal with laundry smelling sour until 2001. I systematically quit using liquid detergent, increased hot water usage, and routinely ran bleach in the detergent trays to try and keep the machine fresh. In my current set which are now one month shy of 9 years old, I never used liquid detergent, quit using FS about 4 years ago, and recently stopped using dryer sheets. I am noticing that discontinuing the use of the sheets has had no discernable effect on static, softness or a clean fragrance fresh from the dryer, so I don't intend to go back to them. I am noticing the towels don't smell sour, so I am glad I quit using the dryer sheets. Still, I never had to constantly tweak my laundry habits like I have had to the last 25 years or so.

Repeated vinegar use may also damage the washer components over time.