I disagree, bonding with older gliders is not any more difficult than bonding with some joeys. In fact sometimes it's easier.
I've gotten gliders anywhere from new born ( born in my house ) to a 4 yr old freshly neutered male, with many ages in between. Age really has little to do with it at least in my experience.
I'll focus on Nicky and Amy for a min since they are closest to the OPs situation. These girls were surrenders from a woman who only got them to be cage mates for the male that she loved and was bonded to. The male died, and she no longer wanted the girls.
They didn't have names, were about 2 yrs old, lived in an aviary type cage made of unsafe materials outside in the Sarasota Fla temps for at least a year, where she just threw some steak and canned mealies in for them to eat. They were never "bonded" to the owner, never used bonding bags, no tent time, no interacting with humans really other than to receive food and water.
They arrived in a very tiny bird cage, a ferret cube with threads all over it and with one raunchy wodent wheel that went directly in the dumpster and a box of canned mealies and pellets that also got tossed in the dumpster.
I was only suppose to be fostering these girls for our local rescue until they had room for them
that notion lasted a whole day, till we picked them up. Once we picked them up we knew they just found their forever home.
These girls took some time and effort and understanding on my part and theirs. They did great in bonding bags for never having had used them before. They adjusted quickly to living inside with AC and new foods. Nicky was a biter for the longest time but has gradually gotten better and I have learned how she needs to be handled so I don't get bit.
On the flip side of the coin, I had a 10 week oop joey that had huge issues being in bonding bags, crabbed all the time at every little thing... the joey was handled all the time by the breeder and was sweet as could be...for her. The girls were never handled and did great.
Every glider is different and how they react to things is unique to THAT glider, not their age and not even their history.
So to answer your questions...
yes I can relate
it took me about 6 months to see significant progress with the girls and to this day continue to see progress and new mile stones in our relationship.
do they ever "bond" yes, I believe a glider can bond no matter what their history was and how old they are when you get them. There is no time limit on friendships and that is all "bonding" really means.
They interact with me like my other 7 gliders do lol, They climb on me pee n poo on me take treats from us, rub on me to mark me and they groom me.
How they interact with other gliders, they are two of the most accepting gliders I have. They have been introduced to hmm lets see 6 other gliders in my home, been in a couple different combinations and recently just accepted a 13 week oop joey into their clan. Nicky despite her size and joy of biting humans lol is a very accepting, nurturing, doting Mother figure in her colony.
What I've learned is this...
1 don't focus on the gliders past. They are no longer neglected, no longer ignored, no longer in need of your sympathy.
When they came through my door, they came home, period, they are now my babies and always will be so their future is looking pretty damn good.
2 If the gliders have a negative reaction to something ( ANYTHING ) Then do that thing differently, until you get a positive reaction. Figure out what works for THAT glider. Like Nicky I can't just pick her up like I can my others, I have to place my hands in a specific way to pick her up. I have to approach her differently OR just allow her to approach me ( which is what she prefers )
3 Don't put any time limits on "bonding" and don't have expectations, negative or positive. Things will develop at the gliders pace. If it takes a week or over a year, it takes as long as it takes and never really stops.
4 Accept them as they are, love them for who they are. Get to know them as individuals, likes and dislikes, what the gliders "normal" looks like so you can recognize something not the gliders normal.
5 if you take measures to improve their quality of life, they will recognize that. It might take some time, and they maybe confused at first and seem to not want to be noticed or have your attention so focused on them, but they will begin to thrive and realize they are now in a loving, accepting home.
Patience and confidence is a must.
Good luck with your new babies and celebrate every bit of progress you make no matter how small it is!