You will get a rebound effect and the GERD is even worse than ever. However, if you are careful how you do it, you can hold the discomfort down until you get used to the new medication.
I quit them after taking them for years. They were great; really did the job. Unfortunately I didn't want to risk the dementia thing, so I moved to Famotidine, 20 mg 3 x a day. I also drink water with calcium carbonate in it if I need to.
If you take them for 3 months, you'll probably have to wean yourself off of them by taking fewer and fewer of the little beads inside the capsule each day. I think it took me about a month or so to get off them.
I have one of the top gastroenterologists in the state as my doctor. He explained the studies, but it's so long ago that I can't recall it. A lot of it has to do with the complexity in constructing studies that would draw that line from PPI to dementia. He actually thinks I should take the PPI. The way he says it is "there's something there but what it is, we don't know." He humors me, however, and goes along with the Famotidine.