I mean what kind of things are you doing to your macbook? I have trouble coming up with ideas for that, like are you scraping it regularly with fork or put some coins into bag with it?How durable these skins are?
How many years remain in good shape and condition?
I bought it to get rid of fingerprints everywhere, it wont protect it from falls and stuff.
For condition, top and bottom should last years, palm rest and trackpad get in contact with oils from hands, combined with how much do you use them, it really depends.