If you follow directions about charging/discharging your battery so you don't kill it prematurely you should have no worries.

Overcharging aka (cooking) or completely discharging the battery a couple of times will kill it early - otherwise you should get years of use out of the battery.

At which point your warranty should be expired and opening the case to change the battery would not be an issue.

I imagine it would be similar to replacing a Macbook Air battery which is also not supposed to be user replaceable either.

N.