I saw a comedian, and he has two children. And he very accurately pointed out, that when one of them goes somewhere for the day, and you're left with one, it doesn't get 50% easier. It gets 100% easier.
It's very different for NT children. My cousin has 3 DC and said to me "Well, DS is 15 now, of course you can pop out if the younger 2 are in bed, instant babysitter! Just like we did with our DD!" And I can remember looking at him and thinking, oh how little you know, and how nice it must be in your world. DS has ADHD, severe. I couldn't leave him on his own in the evening, for what he'd get up to unsupervised, and the very idea he would be able to cope should a little one wake up, is inconceivable.
With DTwins, yes it's easier as they have an instant sibling to play with, an instant best friend, and I feel very privileged to have them. But also, depending on what side of the bed they get out of, an instant arch nemesis. "That's MY ball. He took my rabbit. She ate my pear. He poked me. I want a carry, no I want a carry. He screamed at me!" They are fantastic and exhausting in equal measure.
I have never had a break from them, except their nursery sessions, and when DH goes away for work, he'll come back and say how he's missed them. I would love to miss my children. I've never had the opportunity to miss them, I've never had a night away from them since they were born. Constant dependency, with no repsite, is exhausting and I can see why single parents burn out.
If DH takes one out to the shop with him, it is like a full on break. It's so peaceful. I can't wait for the day they are old enough to go on a school trip, or sleep over a friend's. Where I can wake up naturally, instead of to them causing a hullabaloo, and then straight into dealing with that. I last woke up naturally 3 and a half years ago.
DH keeps saying to book somewhere and go and sleep in a hotel, and I might do that, but it's not the same. It's not my house with all my comforts. I just want to go to sleep, drinking tea from my cup, watching my TV, in my bed, and wake up whenever it may be, without the DC, for one morning.