Does anyone use the Dr. Brown bottles???? If so, do you know at what age to remove the vent system?

@jessicaonate, I was told till they no longer need burped or if you're still scared, then use it with the vent system till they ween! but in the picture, the white top with pink stem leaks without it in the bottle and the green on green doesn't leak when you leave it out of the bottle. just when you decide to take it out. there is no problem with using the vent system till they are weaned. but if you have the bottles that can't work without the vent system vbut you feel you no longer need it, is it really worth switch it bottles if Dr Brown's is all they know? (sorry my system in the pic is dirty I'm in mid wash)