My Kobo only froze once, and that was my own doing (played around with the plugin, which is not official).
Battery life depends on wether you power off the Kobo or just let it sleep. Powering off will get you about 4500 page turns. That's not that much, but depending on how much you read that will last about 1 month.
If you can charge your battery about 500 times that would mean 500 months or 41 years (but the battery will start to lose capacity before that and I'm sure you'll buy another reader sooner than that, too).