I have been looking at finding some door trims in decent shape and see a lot of them tend to warp and crack (being wood), presumably a mix of water and wear and tear.

Is there any tried and tested way for protecting/preserving these? Their shape looks a bit complex to copy using sheet metal. I was thinking about coating them with resin and a thin layer of fibreglass matting.

Opinions?

I've seen guys who cover the entire back of the door trim with fibreglass and you can't tell from the front. If you wanted to be really sure you could always replace the fibreboard with new stuff I guess. To protect the surface I think nothing beats tinted windows and some sort of protectant!