It really depends on how it is used (and abused). I have a 160GB Classic purchased two weeks after the initial release and it is going strong (knock on wood). I also have a 60GB Video (5th gen) purchased December '05 that is also happily playing music (and has since been passed on to my son).
You do not say what happened to your Classic. If it is the battery, that can be replaced for a modest cost (certainly a lot cheaper than a new iPod). Other issues can also be fixed for a reasonable price. There are iPod repair facilities (not affiliated with Apple) that can diagnose and repair (
http://www.iresq.com is one that I've read good things about on this forum).