After that rebuild, the first five recharges went like this: 21, 21, 21, 23, and 20 days. The last interval included seven days of vacation, during which the battery suffered just the usual self-discharge common to NiMH cells.
That’s about what the OEM battery delivered, back when it was new, so the new 600 mA·h cells seem to be about the right capacity. Obviously, the end of the OEM battery wasn’t nearly so pretty.
In round numbers, the wireless charger requires one hour to restore the energy drawn by one two-minute brushing: the thing charges for about 21 hours. There’s additional loss from three weeks of self-discharge in there: if 7 days of non-use = 1 brushing, then the usual 21 days = 3 brushings -> 14% loss due to self-discharge.
I’d take a large grain of salt with those numbers…