I've been told by a lot of vets to ride the weight loss down for as long as it lasts, even if you dip way below your goal weight. Usually the weight loss will taper off by itself unless you have extreme complications, and that breathing room will be welcome when you hit that rebound and gain some before balancing out. At least that was the advice given to me by DS vets that have maintained their weights for well over a decade, so I assume the same holds true for bypass patients.
It is very rare to lose too much, but it is possible that your body's happiest set point is lower than your goal weight, and you'd never know if you don't let the weight loss continue until it naturally tapers off.
I don't know what maintenance looks like for a bypass patient, but I suspect like Catwoman7 says, there is some measure of monitoring and portion controlling that will always be there, just like a lot of naturally thin women engage in to maintain their weights. I figure you either track your food (with an app), or you track the scale, or you track both. But most women I know track something regularly to maintain. I'm so excited for you being so close to goal!!