I get those all the time up here in Oregon... deck joists pretty much start to rot the day the deck is built. Fast-forward 15 years and Mr. Repairman just cuts them off, ususally leaving about 6" to 'sister' the new ones to. Most often, there's half or so good ones left and the repaired ones are just for show.

I usually just ask the buyers if they have heavy friends or ever have 'kegger' parties