I got a bb cradle too... 3 in one charger from ebay one of the best investments. I charge my bb nightly and the battery seem to last all day with active use.
Even before I got my curve, I bought and extra Battery here @ Crackberry it's always worth having a spare around. Lith-ion batteries don't have any memory issues, but they have a finite number of times you can completely charge them. I say charge it when you need to, If I am below 50% when I go to bed I charge it. If anythime I know I am going to use it heavily I make sure it has a complete charge. Watch your bluetooth and GPS apps, as well as any app that auto refreshes. They will all drain your battery quicker.
as a rule of thumb with most li-ion batteries you don't want the depth of discharge to be much more then 80%. So pretty much as long as the battery is over 20% charge remaining then you are fine. and like was said above it has a smart charger and keeps the battery at 100% when plugged in but will not over charge the battery.
