ok girl scout leader and mom of elementary children expert info (not) here I go, from what I remember....
If these were Monarchs they do try to join the migration, which in your case would be moving south to Michoacán, Mexico. Not all of them make it to their ancestral home, some land and lay eggs and die, those babies continue that path and cycle.
It is very easy to raise them, well we had an easy time raising painted ladies (not monarchs) we did it! I can now see how it makes sense to have this be a business. I suspect they have many cycles in processes and if they are ready to ship they pull from the inventory of that date, if they don't have orders to fill I assume they release them in the wild, or save some to produce the next cycle.
The lifecycle is short for painted ladies, I think 30-45 days.
the net that we had was about 2-3 feet tall 2 fee wide. We kept it in the house, Molly's room actually.
It was a great process to watch.
If you are interested you can order the kits online and do it at home yourselves. It was a very calming process to watch and joyful to release them when mature. We had all but one grow from the catepillars to butterfly and they laid eggs before we released, but we didn't have the right leaves for them to eat to survive.
If someone else knows more here, please correct or add to this. It was a few years ago we had this whole process in our house and lives.