It is possible for the suspension to go bad, particularly from the rubber parts hardening, just sitting in the box. This is supposedly a bigger problem in urban areas with high pollution levels (ozone being the main culprit). But, most high quality cartridges don't exhibit such problems. I have heard some cartridges that are more than 20 years old that sound good.
As for stylus wear, a friend of mine has a Lyra cartridge that has well beyond 2,000 hours on it that still sounds very good. If the cartridge has a very high quality diamond and the records that it plays are kept clean, the stylus can last a very long time.
Many years ago, when I ownd Shure cartridges (Type IV, V), I noticed degradation with less than 400 hours of play;, while my MC cartridges have lasted many multiples of that amount of time. I have no idea as to whether this was because of a different grade of diamond used, whether microridge-type profiles are inherently longer lasting, or whether the suspension was more delicate with the Shures. Whatever the case, I am certainly pleased that the really expensive stuff seems to last a long time.
