definitely not. I didn't even use the maintenance packs at all. just went on a 1000kcal diet consisting of fresh vege and some frozen oven chicken or fresh white chicken bits for a good while and my weight kept dropping. back on normal diet for more than 2 years, gaining only around 1kg thats all..that is with some exercise and running included of course.
I think the reason u hear so many horror stories about people putting back all the weight they lose is becauses they go back to their old eating habits. If you re-educate your eating habits, you wont gain back the weight that you lost.