As everyone else had said: gliders have each their own personalities. But bonding is mostly up to you, you have to get to know them and their unique traits, and work with each. Patience is key there.
Age can make a difference in the sense that they have already bonded before, this could be positive or negative. Positive because then they would be used to human contact. Negative, because depending on the glider, they could be more defensive in bonding with another; but this depends on the glider as I said. My breeders run a rescue as well, they've dealt with gliders from all kind of backgrounds: very well cared for gliders, neglected gliders, mistreated gliders, and anything in between. But it is hard to tell how things will turn out at the end. Some of these gliders have become permanent residents at their home due to either health issues or personalities issues (though rare, there are gliders that will always be aggressive towards humans). But I've also seen cases where neglected, mistreated gliders are just hungry for affection and bonding goes extraordinarily well for the adopting family. While I've also seen cases of joeys that are just too stress and are harder to bond with.
Anyways, I don't know what procedure the people you are adopting your gliders from follow; but in the case of my breeders, they like meeting prospect owners and ask them tones of questions. They do this in order, not only to verify that you will make a good home for your new family additions, but to learn what is it that you know and educate you in the areas you are lacking. The other reason is to pair you up as best as they can. My breeders handle their gliders a lot, and get to know their personalities well enough to be able to match you with what they believe will be good gliders according to your needs and preferences. They will introduce you to some gliders they believe is your best match and let you interact with them, they don't even make you take them immediately, they encourage you to continue visiting them until you are sure of which gliders you wish to adopt.
In my particular case, I had originally gone to them looking for Black Beauties (I just love the dark marks on gliders, that's why I wanted BB). In any case, after my first visit with them, they concluded that for me joeys would be best (being my first time owning gliders, and due to my limitations, they wanted me to have the best experience with joeys they had raised themselves). To make the story short, after presenting me with several joeys, at the very end they brought 2 caramel twins, and said they thought these were the best match for me. What can I say? I immediately fell in love with the fellas, and after several more visits (when I met them they were only 6 weeks OOP, and I didn't adopt them until they were almost 10 weeks OOP), we finally brought them home with us, and they've been together with us since.
It is my opinion that this is the best way for adopting. It is never good to rush things, specially when it involves other living creatures. It is best to take your time and weight your options.
Sorry for the long post.