Have you considered installing an automatic in-line booster fan?

from Sears HE3 manual:
VENT LENGTHS
Number
of 90º . . . . . . .Box or Louvered hoods . . .Angled hoods
0 . . .Rigid metal . . . . . 64 ft . . . . . . . . . . . . . 58 ft
1 . . .Rigid metal . . . . . 54 ft . . . . . . . . . . . . . 48 ft
2 . . .Rigid metal . . . . . 44 ft . . . . . . . . . . . . . 38 ft
3 . . .Rigid metal . . . . . 35 ft . . . . . . . . . . . . . 29 ft
4 . . .Rigid metal . . . . . 27 ft . . . . . . . . . . . . . 21 ft

appliance factor,

I had the exact same situation when I got my HE3 dryer. I have a very long run with many turns, and the dryer would run at "8" minutes for a long period of time. I completely cleaned out the whole run and replace the flexible plastic hose behind the dryer with the rigid but bendable metal. My dry times were reduced to less than 30 minutes for most loads.

As time passes, my dry times increase, and I end up cleaning the venting each year.

So perhaps cleaning your venting will help.

Good Luck.

Joe

Do any dryers have a warning light to indicate increased backpressure and therefore suggest vent inspection/cleaning?

If you're sure that your vent line has no built-up lint or other obstructions for its entire length, then a dryer vent booster fan would almost certainly solve your problem. The booster fans from Fantech are completely automatic. they switch on when air pressure builds up in the vent line from the dryer fan running, and turn off when the air pressure subsides. They have both in-line models and models that would mount on the wall at the end of the vent run. More info available at the linked website below.

Here is a link that might be useful: Fantech Dryer Booster Fans

both of the following come in gas versions. The GE Harmony dryer with Adaptive Vent system and the Kenmore Elite Oasis 7.5 cu. ft. with the dual-action drying system. Both of these dryers adapt automatically to different venting situations (length).

chipshot--my Maytag Bravos gives an "AF" (airflow) error code for such situations.

It is my understanding that the latest-model Maytag Bravos have a newly-designed high-RPM blower that allows for long venting.

Correct:

New Blower System info

Bummer for me, since I have the older design that apparently encounters the airflow error more easily.

About a year ago, LG had a dryer model with a static pressure sensor which would warn you. Don't know the model number nor if it's still a current model/feature.

I 2nd Joe in Philly's recommendation to make sure you vents are clear and replace any flexible hoses (even if they are metal) with rigid vents. We also have a very long run with elbows and had a dryer fire due to the lint backing up into the dryer. Longer drying times are a major warning sign that something might be wrong with your venting.