How many video storage can fit on iPhone 5

I have a concert tomorrow so I've gone and put all my data, music, apps, photos and everything onto my computer. I reset my phone and now I have 12.8GB spare

I want to record 2-3 hours since I want to capture a lot of this night. I'll be using a camera for photos though because it's better quality, but only allows 30 seconds of recording.

Anyway, will I have enough GB to record and most importantly is battery life an issue here?

(it's an iPhone 5 with ios7 but I don't know if that makes a difference)

Well i had like 2gb on my iPhone and was able to record for about 30 minutes then i got a memory filled annotation