I know I touch on this in my book, probably in the discussion on blending. Some beers can be saved, some beers are past hope. Some just need to be approached in a new light. Depends on how you want to use them.
Over the years, I've had two beers that were stored for more than 5 years eventually develop a aceto infection, probably as a result of a lazy transfer or filtration. One was a doppelbock, and the other was a biere de garde. That doppelbock took a first round medal as a Flanders brown last year in the NHC. The BDG could probably as well if I entered it this year.
I remember dumping maybe two early batches that were horribly oxidized (wet cardboard) and one that was increibly phenolic (cold steeped spices in the secondary). I don't use those techniques any more