It's really dependant. Some people come off clomid and levels stay "elevated" (new "normal" higher baseline) almost permanently while others jsut see the spike and then drop back to "normal range".
Sadly, it's totally unpredicatble and will depend what your natural test levels were, what your current body is like, etc etc. THeres a billion variables that will change this answer even for one person from one cycle to the next. its never a constant