Hi dosbabe.
This has been my personal experience:
When one first starts induction, it generally takes around 2-3 days to burn up the glycogen stores and go into fat burning mode. IF one subsequently cheats....it usually takes less time to burn up the glucose from this cheat....generally about a day. Of course, this all depends on HOW badly you cheated, WHAT you cheated with, HOW long you continued to eat this/cheat, etc. If it's just a small incident....you'll usually go back into ketosis/fat-burning mode approx. a day later. But if you go off plan for several days...it could easily take you the entire 2-3 days again to go back to fat-burning.
Hope this helped.
deena