I don't do much high heat grilling,more smoking...my WGA is always setup for indirect heat.
About 1/3rd - 1/4th of the coalgrate is used for the briqs and the other part of the grate is covered with aluminium Phoil for easy cleanup.
Normally I put about 10 cold coals and 6-8 hot ones in there.
It'll last for aprox. 2 hours with the briqs that I'm using with the air intakes dialed on indirect.