What is the process for detailing it correctly? My house's wood trim has never lasted more than a couple years after being repainted.

I don't know where you live, but it's abnormal for wood trim to last only a few years. I live in the Puget Sound area where it rains many months of the year. My house is almost 20 years old, and the wood trim -- which has been repainted once when I wanted to change the color -- shows no signs of rot. Proper detailing starts when it's installed and involves priming the wood trim (preferably on all four sides and the cut ends before installation), caulking all corners, intersections, and seams, and giving it two coats of paint. It helps to have eaves, but only parts of my house are protected in that way. Last but not least, it's very important to use a rot resistant species of wood, like cedar.

I have no idea what kind of wood my trim is. I'm in southern CA where it rarely rains. Since the wood is already installed, are there steps a painter can take to make it last better? I've gotten bids from three painters: one uses Bondo, one uses epoxy, and one uses putty. :)

If you want to repair it, my preference would be to use epoxy. If it's pretty far gone, it could be cheaper to replace the trim with new materials. I would be interested to see some pictures of what this trim looks like as it's hard to imagine rot occurring where there is little or no rain.

I'll try to get some pictures tomorrow.

Here are some of the windows, a door, fascia board, and a cover for the basement access. A painter told me today he'd prime and use Bondo for the repairs.

Louisa-

Thanks. That does not look like rotting to me. What it looks like is an older home that has been painted a number of times without proper preparation of the surface, and you have cracking and flaking because the old coats are dry and separating in places, and the newer coats of paint are failing as a result. This also happens when modern latex paint is used on top of older oil-based paint without proper prep.

The way to fix this is to have a painting contractor do a pressure wash to remove loose, old layers, repair any spots that actually have damage or rot, sand everything, prime it, and paint it. Unfortunately, this won't be cheap if it's done properly, but it will last a long time.

For the windows and doors, I would use an epoxy filler instead of trying to replace any wood. Even with the existing damage, the original wood is still better than replacement paint quality wood. However, I would just cut a new access panel rather than trying to repair that one. Old houses sag and move and much of that damage may come from trying to open stuck windows and doors. You may need to work on adjusting them to avoid similar problems reoccurring

Thanks, kudzu9 and Lyndee Lee! Your advice makes good sense.

Yes, yes it can. Whether it works is another question. I have used it quite a bit to seal the insides of large hollow exterior trim assemblies (old timers used pitch for that) , and to completely seal end-grain, which it did a fabulous job of doing.