Genuinely curious. I'd like to use a phone with a hardware-keyboard as my daily driver too, but the only ones I can find are so old their batteries have worn down to the point of being functionally unacceptable.
I have bought a new battery twice, and the last one I have lasts about 1.5 day or so and I bought it maybe a year ago. I am not a heavy user but you can still find the battery on the market - the one I have was made by "Cameron Sino", model CS-HDE160SL, it's Lion battery with 1150 mAh (as they claim). I bought the G1 pretty late, I think two years after it was introduced, so I have it maybe 8 years now?