I bill for hours and I'll definitely go and refactor something - but only if I need to touch the code anyway in order to implement a new feature or fix a bug.

I'll fix _every_ bug the right way, the first time; that may involve refactoring underlying design weaknesses that caused the bug in the first place. I also make sure that this or a similar bug don't happen, which also may cause refactoring.

No one's ever complained... I guess that's because it's actually very time efficient in the medium and long term, and usually also in the short term.