Basicaly I don't want to Refactor because I can. I want to do it becuase it is the correct thing to do.
Therein lies the problem... there isn't a hard and fast rule... only general guidelines and gut instinct. A lot depends on the situation. The rule of thumb Nick pointed out is generally how most of us deal with it... but even with that, there are times when to break that thumb and do it another way.

-tg