I would say that if you feel as though you can't take care of them properly, giving them to your friend may be a good option. Especially if his/her glider is self harming due to being lonely. Your gliders may even enjoy having a new addition to their colony.
I've contemplated giving mine away as well, I've only had mine for 7 months. Im a recent college graduate and an in the process of buying a new home, etc. but I've bonded to my twin boys and they've bonded to me. The thought of getting rid of them is just a slight thought, I'm not going to. But I feel like you've already made your decision. You should do what's best for your gliders and yourself in the long run.
They definitely need interaction with their owners, but in my opinion gliders need each other more than they need us. So you not being able to spend a lot of time with them isn't the worse thing in the world.