Each time you rack, you add a little oxygen to the wine. Oxygen is what sets off oxidation, so you generally want to limit it.
I wouldn't rack more often the once every 6 to 8 weeks or so.
I only make grape wines. I bulk age my wines and I generally add a clearing agent to start clearing. Once I add the clearing agent, I generally won't rack more than 3 times over the next year, depending on how often I get a new sediment build up and that varies. One of those rackings is at bottling time; I always rack before bottling just to make sure... nothing worse than getting down to the bottom of the source carboy and finding there really was sediment that you didn't see.