Let me just play Devil's advocate a bit here.
There is a point of diminishing returns on clarification in the secondary. For most beers, I'd say that by the time it's been in there 10-11 days, it's probably done *almost* all of the clarifying it's going to do. The nice thing about carboys, of course, is that you can watch and monitor the process. If it doesn't appear dark and quite clear after a couple weeks, then sure, go ahead and leave it longer.
But you'll also generally get very good results from 1-2 weeks in the secondary.