I don't know what to suggest as to keeping them on but I will ask, is it necessary that they have them? Are they indoor cats and the collars just for decoration? or are they outdoor cats and the collars hold their tags?
My cats get them off at least once a week, I just keep putting them back on even though they are indoor cats I think that if they ever got out the more info on them the better, not everyone would check for a microchip.
Beastie bands seem to stay on a bit longer than regular breakaways for my lot.
A microchip or a tattoo, or both, should help your peace of mind. I would recommend them even for indoor cats; they do get out once in a while, just check our SOS section.
Many cats just won't keep them on. More proof that they just have their own minds!
My daughter puts a collar on her outside cat and she's always taking it off. I don't know if there is an answer to your problem. Mine are microchipped and are indoor cats. I don't have small children to let them out and I live alone. So It's unlikely they'll get out. But others who have said not everyone looks for a microchip, is right. It's a bone of conention with me that even a shelter may not look for that valuable chip.