Leaning / step climbing?

Hi all:

I fly underneath a Class B airspace (Washington). My question is that
while I am leaving the area on a flight, I will often end up climbing
up higher as I get further from my departure airport as I get under
the shelves that are higher up. When I am entirely free of the Class
B, I pick a VFR cruising altitude that is appropriate, and at that
point I lean the engine out on the 172. My question is, knowing that
I will have frequent full power applications to climb out to higher
altitudes, 1000 - 2000 - 2500 - 3000, etc., should I lean at each
altitude, or is it better to just let it go until I have stabilized at
my cruising altitude and then lean accordingly?

aw