Welcome to the forum!
They will not eat untill they burst, they do get full at some point and will refuse the food. But that does't mean you can't overfeed them. I find everyday feedings make my axolotls fat (the body wider than the head like stated above) where a feeding is as much as they can eat. Mot people feed their adults as much as they can eat in a few minutes or untill they refuse the food, once every 2-3 days. They should stay a regular weight then unless you are feeding a high fat food like animal muscle or heart, which are only recommended as a 'sometimes food'. That or i find a small amount of food every day will keep them stable. So one or two worms maybe. I think its best to find a routine that suits you the best as long as they are not starving or obviously eating too much.
a stable weight adult axolotl can survive months without food, they are built to be opertunistic feeders. so dont worry if you forget to feed them once in a while
baby or juvinile axolotl have to eat a lot more because they are growing. So if your axolotls are under 6 inches feed them as much as possible!
good luck