Yeah, I think you might be right although AFAIK they still hold on to about 80% of their initial charge after that time (10y), which is quite a lot. 30 years wa

Yeah, I think you might be right although AFAIK they still hold on to about 80% of their initial charge after that time (10y), which is quite a lot. 30 years was just a random thought that seemed like a sensible minimum to be somewhat low-maintenance solution. I am just trying to think about different possibilities, they pros, cons and what might be net win in this case. Your remark on people not wanting to service yet another thing is spot on, grid always works for them.