My mom did it for 6 months and lost 50 pds.. After doing it that long it just becomes a way of life and it quite easy to maintain. I know she got off track a bit.. but maybe only gained 5 lbs.. and that was 8 years ago..
Just keep on track with it and remember that you hit Plateaus (SP?).. and it sometimes takes longer than others depending on your matobilism and countless other things.. I know from personal experience that weight watchers is well worth it.. But it works for some and not for others..
Good Luck !
It is VERY hard to lose weight!