Is this normal for iPhone 4S?

The battery runs out pretty quickly, I unplugged it at about 9:30 and by 10:30 is was 88% I was in the phone to someone till 1 pm and it went down to 15% and then I was talking to him and I went on snapchat and it's down to 5% in 15 minutes, is this normal because I was on the phone?

Normally it lasts about 7 or 8 hours before needing to be charged and that's me using it loads, I literally text all day and I'm also using a lot of Internet apps, is that normal?

If you've had it for a while and you constantly have apps running, then obviously the battery will start to deteriorate a bit.
It's normal.

Yes. Most of the phone was upgraded, but the battery life was downgraded.

Yes the battery does run out quickly but it depends on what you are doing with it. If your on the Internet a lot it will run out quicker than if you weren't. This also happens if you are on an app that requires a lot of storage space.

If you do the same thing all the time you can "train" the battery to the point that it will not hold a good charge any longer… Start charging it halfway through, one third through, mix it up, instead of waiting for it to deplete totally…