Do you trust Airbnb self-checkouts?

[bombastique]

I'm doing Airbnb for the very first time as I am spending more time with a friend over the holidays.
I was there to see welcome my guests and check them in. I asked them to put the keys through the letter box.
Now I'm in two minds about just going back to ensure they check out.
Anyone with Airbnb experience? Do you trust guests to leave when they are supposed to?
Thanks.

I have used AirB&Bs a lot and never had the owner come over on checkout. Quite often you let yourself in and out but even those that want to meet you on check in dont come for checkout. I dont think I would book one that did. We are always out by the checkout time but don't want to hang around if we are ready earlier than a pre agreed time.

Yes I do trust guests. I've not been doing it for long (8 months or so) but haven't had a bad experience with a guest. The review system helps, everyone (guest and host) is on best behaviour.

Thank you for the comments. Very reassuring.
I had to hand them the keys on check-in as my flat is in a highly secured building and there's no where to leave the keys.
I will leave them to check out. I've told them to pop the keys through the letterbox and I'll pick it up when I return.