My cheap Maplin ones are quite old (obviously) but keep the mouse happy for a couple of months at a time. The 2000 mAh ones are best, they must self-discharge slower.
This is with a Technoline charger, the bog-standard NiMH charger I used to use wouldn't get two weeks out of them.
According to Mr Technoline, 10 years on, his BL700 is still a best seller.
Given that both of mine are that sort of vintage, and that they are *on* all the time, they're not doing too badly.
Incidentally, if anyone likes to talk batteries, feel at liberty to give Mr Technoline a call.
He freely admits to talking batteries with a passion and, thanks to online shopping, bemoans the fact that that particular delight is largely missing from his world. I don't get the impression that he is picky about battery type.
Batteries that aren't recognised are typically below 0.7V. They can often be resurrected by a charged battery (or a dumb charger). The trick with the charged battery is to connect them in parallel (piece of foil on a worktop, stand the batteries side by side with the -ve terminals on the foil, and then place another piece of foil over the +ve contacts). The charged battery acts like a charger and you can get enough in over a few seconds that it will then briefly register sufficient voltage to wake up a smart charger, if you transfer straight to the charger.
According to Mr Technoline, the difference between the BL700 and the newer BL700n, is that the newer model
will recognise batteries which have been run properly flat, and attempt to recharge them.