You need to do what is right for you. If you stop today then you still accomplished a great feat. If you make it to day 7 that's wonderful too. If you go on to day 12 then that's fantastic. You must listen to your own body.
I don't think that you should contrast & compare your master cleanse in terms of days completed, weight/inches lost etc...etc...I think that no matter what the reason for doing the mc you should be proud of what YOU accomplished.
I've never made it past day 8. And while I'd really like to go longer I;m not going to berate myself if I never do. I will however keep trying. But everyone's body is different. Mabe you do not have that much to get out of your system. So maybe 6 days is all that is neccessary for you.
Besides your body, listen your heart & to common sense too. Common sense is always a welcomed friend in these matters. ;~)