Sure as sure can be with the figures. They are both heavy aircraft and they are both old. Yep I lean them off and on average run at 65-70% power. I usually fly them on maximum weight as well, I don't see the point in flying 6 or 7 seaters with 2 or 3 people in them.
Oh and I am glad your sceneca has 2 engines
I went up crop dusting with my mate in states in a Sceneca....that was fun.