I eat porridge with a bit of honey about 3-4 hours before and then a narna about 30 minutes before.
The one recommendation I will make is treat your long runs as marathon day training. Eat what you think and see what works for you. Its the only way to know that it won't upset you and what works for you.
In marathon training the LSR is about getting miles into your legs. When you are running 15+ miles you will be on your legs for a while thus achieving your goal however when I am running sub-15 miles the temptation is to go out too fast so I will make sure I slow my pace right down to ensure my body has to work harder (practice providing me with energy).
The distance one week, time the next, as Lee says, is a good idea if you get bored.