All of my Innokins, including the ones with fixed internal batteries lasted from 1 - (4+ so far and still going) years.
When I switched up my tootle puffing to more modern standards (40-60 watts, still pretty tame) I switched over to Wismecs because I have hand problems that make the buttonless/squeeze operation a lot easier for me to use, and stocked up on those since the same hand problems mean I can't deal with the weight and diameter of multi-battery mods. So far the electronics on the Wismecs have held up, and I love the squeeze to fire switches, but the physical battery cover closures on both the RX75 - magnetic, but the little magnets come loose and the Sinuous P80s with little mechanical slide grips that bend and/or break have reduced what I was hoping would be a lifelong supply* down to maybe another years worth.
So I'm not sure what I'm going to try next - I'd stock up on even more of the Wismecs but they're obsolete now.
* I'm 69 and not a healthy active 69. The funny thing is I got hit with a spinal cord problem that seems to be entirely random - not connected at all to smoking or weight.