from the gliders we have had I would say, one or two, does NOT matter.
young or slightly older will bond no problem. their past life may slow down or speed up bonding depending on how friendly they were treated.
Think of bonding as a "trusting" of you. they will start to think of you as a friend and NOT a foe. Just like many other animals. My dog spent his first night at the front door trying to go back home. But with the dog he found out we are his friends in a day or two. With a sugar glider it take weeks or months. Each one is different and each one will start to trust you at its speed.
since we have several gliders, some don't get the one on one time that our first few did. But scarface is still making progress to trusting us, just at a much slower rate. Her brother Riggs was much faster to trust us, he will jump on us after a treat and then run away down the hall, while scarface will retreat into the cage if she thinks treat time is over. Riggs will come back to me and eventually climb back up my arm, usually for a treat. While scarface has to be picked up, but she no longer bites.
the more time you spend with them, the faster they will probably trust you. I would recommend as much nighttime playroom time as you can take, maybe a few hours in bonding pouch during day, and maybe if they dont bite a half hour of hand in sleeping pouch, then you just need time and patience.
my wife's bonded glider gizmo spend ALL day sleeping in her shirt, refusing several offers to go back into cage, I took him at 10pm and finally woke him up at 11:30pm and forced him off my hand and back into cage cause I had to sleep.
this morning the gliders where still awake at 8 am, and wouldnt go to sleep in my wife's shirt, so she had to leave without him for a road trip.