My Dual Shock/Sixaxis controllers seem to fully lose their charge quickly when not being used. I last played my PS3 till the last firmware update (in February) and I went to play yesterday and all 6 batteries were discharged...
After less than 6 months all 6 batteries had completely lost a charge. In normal use they usually last 20+ hours I think, but when they are not used, they appear to lose their charge quickly...