If you look at the schematic, you will notice I am powering the promini via the VCC pin, not Raw, so the onboard regulator is bypassed. The battery never sees more than 4.2V from the max1811 charge control chip.
The promini goes into power down sleep mode after waking up from a button press and transmitting the character via virtualWire library.
The battery lasts about a month between charges, when I notice that it is not sending anymore I plug it in to charge it.
A battery disconnect transistor would probably be good to keep the battery from overdischarging.
At the same time, it's been running like that since ~Jan 2011. Maybe battery life has been degraded some, I don't monitor it all that closely.