first MC soon...

i want to start my first Master-Cleanse soon. i just have a few questions.

are you supposed to do this cleanse until your tongue is pink? or does it not always go pink, even after 40 days? i don't know how to figure out how long i should do this cleanse for. for my first time, should i just do the minimum 10 days? (i'm 19, and a little underweight, if that affects anything).

on most laxative teas it says not to take them for longer than like a week or something because they can cause dependancy. if you take them every day on a 40 day cleanse, is that gonna be a problem?

thanks for any help.