Depends on the size of the tank. But it definitely doesn't hurt to overdo it. If it's too much, the heaters will be off, so it's not exactly a waste of power.
I plan to run 1-2 gallons an hour into my 120 and 2-3 into my 220. Doing the math and that's close to 50% a day, minus whatever percentage of clean water ends up being taken away by the overflow.