Gonna depend on time frame and who your dealing with. My game in June 42 (as Japan), I regularly nuke the Chinese with my Sally bomber force for 3-600 losses per day. My bombers fly at 8000 feet. Using 4 bomber units of roughly 36 each. They do eat up supplies. But I hardly take any losses.
Against the other allies, it gets rougher. I still will fly at 8000 feet or so, for bombers but except for the repeated nuking of Rangoon troops early 42 I have been unable to smash up allied ground forces. Flak hurts more too.
Sweeps I try to come in at 2 altitudes if I sweep with 2 fighter units, one at 15,000 and the other at 20-23,000 feet.
But I am far from expert, as even though I have had AE since release, real life kept me from diving into it, so this is really my first serious foray into her. Lots have changed and is taking getting used to.