its not a problem, its not an option. You throw them away after 10 years. First i was reluctant on that part with ‘what iff battery dies sooner’, but its freaking energy effective that i trust the 10 years by now.
if i check the review and also the forum, after 2-3 years batery are empty 
and that is this a Problem for me… and also for antoher people that open it to try to change with antoher battery
that doesnt sound good, but i have no such experience, wonder why it would be such big difference. (bad zwave networks and forced polling would cause this, but with these sensors i have not that need at all)