It is entirely dependant on the pull of your ff and pump, and the capacity of your battery (memory: batteries tend to do better if you totally discharge them before re-charging them). Having said that, If all is within normal limits it should last all day long with a timer running reasonably often.
my .02
btw, a couple of my 7ah batteries out last my 10ah batteries by 4-5 hours of use!!
go figure.