Is 2 hours possible? (Lipo receiver pack run time)

[portyansky]

So I got a lipo receiver in the Mugen. The last race I ran it was a 20 min main and I only used 300mah and its a 2020mah pack!! And that also includes some warm up time and a few practice laps, but lets say 20 minutes b/c its a easy number to work with.
So if I use 300mah in 20 min then that means I will only use 900mah in 60 minutes and 1800mah in 120 minutes. I just dont remember whats the deal about running the lipos down so low.
Reason I am asking is b/c I am gonna be doing a 5 hour (thats right, 5 hour) truggy endurance race. 1 team of 4, one chassis. Not having to come in for 2 hours for a battery change would be amazing!
So my question is, do you guys remember how low I can run the lipo?