lithium ion, li-on, batteries are not like nicd or nimh batteries. Those older types of batteries prefer to be discharged more before charging
ps vita uses a li-on battery, so for maximum battery life or capacity over it's life, try not to drain the battery so much. I have no idea how long it'll last by charging it whenever, I just know that it will last longer if you keep the battery level higher before charging.
With any modern rechargeable, non replaceable battery, you should power cycle the battery at least once a month. That is, let it run down to about 5% or so, then charge it back to full.
but is it important to have it fully charged each time as well? meaning let it fill up to 100% and not any lower
just wondering in case one day i'm in a hurry
oh also another question, does the Vita do some sort of a bypass with the battery when it's fully charged and plugged in? like the PSP? i can only guess so, if u ask me but i'm not certain
so it leaves the battery alone when fully charged and plugged in?
Yes, it does. This is also indicared by the light.
When charging the (PS) button will glow a steady orange, and turn off completetly when charge is complete.