I have used after-hours-returns with Hertz and National and never had an issue. YMMV. If there is a garage, especially a hotel garage, I wouldn't worry.

I do, however, recommend taking pictures of the vehicle when you drop it off. Snap a shot of the dashboard as well, showing odometer and fuel level. The only issue was that sometimes they forget to close out the contract, but that has happened to me on in-person-returns at a small station as well. I watch my email the next morning and call the station if there's no email with the charge details. Last time, they asked me for the odometer reading to compare that with their records, so my picture came in handy.

National told me that they only bill to the end of their office hours, even when you return after midnight.

Hertz contracts, IIRC, state that they will charge you until the time they reopen - which is understandable. But just the other week they used their previous night's closing hours on my rental, just like National does. (It did not make any difference to my total cost.)

HTH