The reality is you have to be economical with your positioning. Save your energy, because you want to have something left in case the last match turns firey.
Avoid foods that drain your energy (such as foods high in salt), and just stay well hydrated. If you have to delay a match for a few minutes while you recover, so be it.
In Australia, even in the middle of winter the sun can have a bit of heat to it, and I could be doing up to 5 matches a day (combo of juniors/O35, lines/middles). I'd wear sunscreen and a hat (anything to reduce the impact of the Sun, I figure that pays off over the course of the day).
On those days, in the early matches I run as little as possible. It's just motivation for preempting play effectively.