A DUI stays on your driving record forever. It also stays on your arrest record forever. The only thing that does come off is after a certain period of time, you can be eligible for regular insurance rather than SR-22.
A DUI conviction can cost an incredible amount of money because you have to look at the fine. You have to look at the probation fees. You have to look at the court cost. Then you have to look at - and you also have to look at the alcohol safety class. Then you have to look at the other ramifications: the one-year use of the airlock. There are all sorts of things. It's hard to put a precise price tag.
I think I read once on the Tennessee Department of Safety Driver's Handbook that a DUI could cost you up to ten grand in fines and fees and court costs, but it also depends on the level of the second or third offense, because the fine increases. It is a significant amount, and it's nothing to sneeze about.