Here's some PS Vita battery saving tips, mine lasts for a good 5-7 hours.
Go to Settings, turn off Bluetooth at Bluetooth Settings in Network. If you need it, turn it on only when needed.
Do the same for Wifi.
Turn off System Music, and the notification alerts except for the first one, so the PS Button and the Sound.
Turn brightness all the way down, or if that bothers you too much just a little under half way.
Go to Location Data and turn it all off. Location data is not needed and updates in the background if you have 3G or using Wifi. I turn it on only when using Near and then turn it back off.
In System, turn off the Auto-Start Settings. If you wanna use them, turn it on yourself, no need to waste your battery.
Auto Standby should be put at 1 minute. 3 minutes most if it bugs you that it turns off so fast.
Go to Group Messaging, go to Settings (in the group messaging) and turn receive automatically off. It updates in the background and is a killer.
When not using an application, close it completely. If you leave an app like PS Store, Video, or a game open while not using it, the LiveArea screen updates and yes, it does kill your battery.
Turn the volume completely off when not using the volume, like if you're just checking into pspmod on your Vita. An easy way to do it is to hold the - and + buttons and the volume will mute. Just leave it around where you like it so it won't be a nuisance when you want the volume back on and back off.
That's all that I know about, I'll let you know more if it comes up.