Motorola Q battery woes

After ruining my previous cell phone with an ill-advised "trying to read a text message while washing dishes" incident, I recently picked up a used Motorola Q Black on eBay. The battery on it seemed kind of crappy, and I just figured I needed a replacement battery since the phone was used. Picked up a standard-sized replacement battery at a local shop.

This is Day 4 with the new battery, and it can't hold a charge to save its life. I woke up this morning with a full battery. I made two phone calls today, neither of which was more than 10 minutes long. I haven't texted anybody. I haven't used any other applications. And still, I'm down to half-full already.

This is my first PDA-style phone, so I'm not too familiar with battery life expectancy on these things, but I do know Motorola Q phones aren't known for having especially great battery life. Still, this seems a little ridiculous.

A couple questions:
1. Is this battery performance (or lack thereof) normal in Motorola Qs?
2. Is there anything to do to get the battery to last longer? (I've already tried charging it when it's turned off, locking the keys and turning off unused programs)
3. I saw an extended life battery w/cover for $9.99 on Amazon. How much of a difference does this battery make?

Thanks.