live mealies are like glider crack, they love them with all their hearts, but they are fattie treats.
dried mealies can be got at petstore or Walmart bird section, they are cheap, will last forever, less "gross" factor and gliders still really like them.
the age of your gliders should not matter, I don't think.
We have 2 out of 10 gliders, that we still have to do a little chasing to get them out of playroom and back into cage. but if I shake the treat bag scarface comes running to front of cage, will eat out of my hand, I can pick her up she just doesn't like it much, will give me a little bite. Mary is a long difficult project for us, she is coming around very slow.