For many years Nevada Music has traded with used musical instruments and equipment and over time has gained expertise and knowledge in this area. If instruments are well maintained and looked after, there's no reason why you can't get a lifetime of use out of them. However, some folks like to swap and change their instrument as a new guitar or bass can sometimes bring new inspiration. Alternatively, perhaps the Flying V that you bought as a young twenty something doesn't quite have the same appeal now that you're thirty something with a couple of kids ?
The other observation regarding second user instruments is that the choice is somewhat diminished when compared to twenty or so years ago. Musical Instruments and accessories have now become so economical to buy that many musicians who formerly could never afford to buy new equipment (and therefore had to search within the second hand market) can now easily afford to.
There are still some second hand gems out there if you look closely enough, but they're not as abundant as 10 or 20 years ago. Nevada has a range of second hand instruments and equipment for sale, so be sure to check them out before deciding to buy.