If they offer a warrantee then you'd hope they last at least as long as that - otherwise they'd be getting so many returns it wouldn't be worth it to them.
$600 for a set is cheap though, so you wonder where the corners have been cut to save so much money? If you're happy with them only lasting a year then go for them. If they last any longer than that then it's a bonus.
After all, there's nothing to say that they won't last as long as OEM wheels, but I'd guess that's down to how they're treated (e.g. not kerbing/scuffing them, not hitting potholes, not speeding over speed bumps, etc.).