Normal checkout is around noon, after which housekeeping will do their magic. While they generally don’t need a whole lot of time per room, they usually have A LOT of rooms to cover, so this can take a few hours. So checkin at 6 is reasonable.

However, there is some leeway there. Returning customers can usually request a later check out. I do this often so I don’t have to haul my luggage around at the final day of my business trips. On top of that, I usually phone ahead and ask if it’s possible to check in early if I arrive relatively early in the day. Otherwise I’ll just take my luggage with me to work and check in later.

This depends on whether they have available rooms. If they’re fully booked, there won’t be any rooms ready until housekeeping has done their thing. In the same way, late checkout can mean that the room won’t be cleaned until next day, unless housekeeping can schedule it for last on their round, so they would need an extra room for that.

It basically boils down to the fact that if they have the capacity, then asking nicely will usually get you a long way.