The only time I change run levels is if the environment I am using is updating (kde, e19, etc) gcc, and some other libraries I can't think of at the moment.
If I didn't change run level, and something were to go wrong, yes, chances are I can fix it, depending on if I have coffee or not, some users can't or have no clue, nothing wrong with that, just be safe than sorry.
I have been burned in the past with major kde updates, I think kde3 days iirc, but other than that I just open yak and du away