So, you know that whole "30 days" thing?
WRONG. There are no science studies or anything done to absolutely prove this.
I did a little experimentation on myself. I smoked for (atleast) 2 months straight, everyday. I am a girl weighing around 135, and I do some light exercise and I was clean in 20 days (or less) with a home drug test (which is scientifically no different than any other test).
Point: If you give yourself a few weeks to get clean and start from a new point, you could smoke lightly every day, just keep the fluids moving and do some exercise, the cannabinoids would never collect and you will, in theory, always be clean.
It doesn't stay in your body very long at all. Everyone's body is different, so it is a REALLY good idea to experiment for yourself, a home test is 15 dollars. In the end, it could save your ass. Make your own discoveries.