Hello, I have 4 gliders myself and each one took a different amount of time to bond. None of them were re-homed, and they were younger than yours when I got them. Your gliders already lived somewhere else and had that world ripped right out from under them. Just keep in mind, 3 months in a 2 year period isn't that long. It will take a while for them to adjust and get to know you, but once they do feel safe with you, it is a wonderful feeling. So don't give up, they can sense your feelings too.
My best bonding weapon is meal worms. They look at with glowing admiration when they know I have mealies :). Also, have you ever tried putting them in your shirt? I use to put them in my shirt ( in pouch if you're scared of getting bitten) and just do things around the house. i spent many hours with a glider somewhere on me and still do. Lots of gliders prefer not to be picked up. It's more like them holding you if that makes sense. Try to hide the palm of your hand and approach with the back. This way, they don't feel like they're about to get grabbed.
Have you tried tent time? Seemed to help with mine.
Hope this helped some. Hate for you to feel discouraged. It sounds like they really need you