Will I gain the weight back?

How many of you have lost a significant amount of weight (20kg+) and kept it off (for more than 7 years)? I have lost some weight (17kg) and I still have a lot to lose (19kg) to be in the normal bmi range. I'm doing it slowly and by changing my lifestyle one bit at a time. I have also stopped certain medication, which I assume also contributed to me gaining weight and then losing it again once I stopped taking them. But the more research I do the more experts I find who say the long-term success rate of weight loss is incredibly low and most people end up gaining all or more back. I'm terrified of gaining the weight back! So I was wondering if any of you managed to beat the odds and kept the weight off for more than 7 years? 7 years because I read that this is how long fat cells live and if you gain weight, they not only increase in size but also in number. But after seven years of not being used they would then disappear. This might be complete nonsense though