Most "dumb" watches that cost over $350 will retain the majority of their value well past those 5 years, too. Apple's first generation watch will be ~$50 in 5 years.
The first Samsung Gear watch was only announced a year ago (Sep. 2013), and you can get it for <$150 new. Pretty sure it will be well under $50 for that model in 4 years.
A $500 watch will certainly still have much use 10+ years from purchase.
It might have minor scratches but that's it.
A smart watch will probably not even power on 5 years from purchase (due to bad battery); or be able to pair with your phone (new phone OS might not be backwards compatible).