has anyone ever had to replace thier PDA's battery? if so, how much of a pain in the ass is it and can you do it yourself?

if not, how long have you had your PDA and what do you recommend to extend its battery life?

I'm not sure what you have... but I've got a palm Vx (Lith-ion). I've had it for 2 years and my battery generally still lasts a full day of use, which includes 1/2 hour of reading ebooks on the train. I installed a hack to underclock the processor, which extends battery time.