You can't compare wellbutrin to prozac. Prozac is an SSRI and you can usually not see positive effects until maybe 5-6 weeks. Wellbutrin is a different type of med (it's actually a psychostimulant), some effects come within days. It was made to replace amphetamines back in the days.

When it is used to stop smoking, you can cease smoking within a week, when used as a stimulant, it works from immediately to maybe two days. For it to work as an antidepressant, maybe 2-3 weeks. Time for it to treat anxiety, never, because it is not meant for that.