One thing I can tell you is that FRA is HUGE and you might have to do a pretty major walk to your other gate. I don't know when your trip is, but if you can keep your coat in your luggage, do it. I was so hot and sweaty there, just having to walk from one of the food places to my gate.

Also I think it's good to break up flights that long if you can. I'm sure some people would rather go 15 hours straight through, but if you're nervous about the length, 7-8 hours goes a lot faster than you think. It's not enough time to get really restless, but the downside is you might not get a lot of sleep if you're trying to do that.