My sixtie five year old fishing boat is still going strong, all the timbers are original. Interestingly the Federal government here just bought out a heap of fishing licenses and paid fishermen $25,000 to destroy their boats {if they wanted to}. My mate with a smaller GRP boat had it moved to a local dump and paid a bloke to destoy it with a bulldozer. He was amazed at just how difficult this was to do. He had to take a series of photos to document the destruction to get his money.
My first boat, a Westerly 25 called Arghiro, will now be 38. I believe she is still alive and well on the E Coast of Scotland. My current boat is a mere 34 and still worth more than I paid for her (over 20K). I see no sign of deterioration of the structure, lots of fittings and equipment have needed replacing (and continue to need it) but they are easy and cheap enough (relative to total boat price) to keep fixing.
I'm pretty sure she'll see me out & provide a fair return on my investment of time & love by providing me & the family (third generation now) lots of happy times.
I did once salvage the fittings of a cadet dinghy and burn the rotten carcase. But problem is that the fittings of boats in that state have relatively little value due to their age and condition.
Old boats end up on the slip at Gillingham Pier. Where a grab lorry smashes them up, rips out the engines, shafts and any other large lumps of metal, which go into a skip, for scrap, then the rest of the boat is smashed up again and taken to the landfill.