Years ago you could stay on Lipotrim TFR until you got to your goal weight but now it is until you get to a healthy BMI 25 then they recommend if you still want to lose more weight of switching over to the Lipotrim maintenance products.
Your friend is probably thinking of the Cambridge Weight Plan or one of the other vlcd's where you can only do TFR (called Sole Source on Cambridge Weight Plan) for 12 weeks and then you must have a week where you add a small meal of 200 calories...after the week is over you can go back to SSing again.