Ikea "Parasoll" Door and Window Sensor Battery Life

[Dave21w]

Is anyone already using this sensor, I bought a few and the first one that I fitted didn't last that long, probably only a couple of weeks. I'm using the Ikea Ladda AAA battery rated at 750mAh. I noticed it was not responding and when checking in Z2M despite saying off line thebatteyr was still showing as 72% when I removed the battery and checked the voltage it was 0.7v.
I suppose I could have a duff cell that just suddenly died but it just seems a bit weird. I did see a post somewhere (not here) when I was searching for battery life info that people said using ZHA the life was poor but when switching to Z2M it was then OK.