Are you always connected to power? I kept a few old laptops that would be practically useless today, but always wanted to resurrect for simple offline things. The biggest issue I have is power when off the charger.

I think my best laptop is 45 minutes or so per charge. At one point I even bought extra batteries and kept them safely stored and dry, only to realize that this does almost nothing to preserve their longevity as now years later I find them all to have about the same lifespan. I have extra 18650 batteries, however Im not sure, given the size of these, that this is what they use in there.