Do I need more than one battery for my Nikon d3100?

I have one battery but I completely drained it in like 45 mins filming some of my friends band concert. (like five four-five min videos) I'm going on vacation in May and I really don't wanna loose battery while at an all day event and unable to charge. Wouldn't it be nice if I could just pull out a second fully charged ready to use battery from my purse? I think yes.
Your thoughts?

Absolutely! Get that second battery! And the real thing, no cheap third party knockoffs! Especially if you're a beginner, you're going to be using most of the battery draining help stuff A LOT. And a lot of battery draining flashes and using the lcd screen letting all your friends review all of the clips. You've seen how fast the battery drains w/ that style of usage. Second battery is absolutely necessary as well as smart.

You should've bought the second battery when you bought the camera. Of course you should have a second battery.

Seems like a no-brainer to me then.

I have 3 for my camera.

I have a second battery for all of my cameras. It is very convenient.