Can you not get them to sleep nicely and then lock the door though?
Crying for 3 hours would give me a major headache.
Some kids don't sleep nicely
My nephew has to cry before he sleeps, it can go for 30-45 mins but if he's so tired it takes a 2 mins cry. SIL has to literally pin him in bed to get him to fall asleep. He screams so loud, then he falls asleep. He's 2 yrs. he will not take cuddles, or soothing. He will end up hitting his mum. She holds him in place, ignores him until he's done crying himself to sleep. She bed shares, she's with him but she leaves him to cry, it's the only way that works.
For us the only way that works those days is to take him for a car ride. I tried everything, & I still bed share, but nothing was working. So now if we're out, I change him in the car & I even carry a tooth brush with me, if he doesn't sleep by the time we reach home, we go round & round until he finally falls asleep. When we're at home, when it's bedtime, we go for a car ride around the building, he even needs music on to sleep, we have to play the same song again & again, & windows should be close. He also wears his sunglasses to sleep in the car
I'm rambling here, but what I'm trying to say, some parents do get desperate when they have ongoing sleep issues. After almost two years of broken sleep, & very late bedtimes, we finally found a way to get him to fall asleep without spending over two hours in bed trying to settle him. He used to cry, have tantrums, leave bed & stay awake until 3 am refusing to go to sleep. He doesn't nap & he wakes up so early. Now he sleeps at a decent time & he gets 9-11 hrs of night sleep.