You're right in assuming that removing the AC belt will remove parasitic drag
from the pulleys. Thereby improving acceleration and gas mileage slightly as
well.

You are also right in assuming that turning the AC on once in a while
circulates the oil in the system to keep your seals supple. However, running
your AC when there is something wrong in the system (such as not enough
lubrication) can be as equally damaging.

Pick your poison. I just spent the bucks to fix mine. I run it daily in the
often foggy streets of San Francisco.

BenT