In principle, absolutely. The only times I can think of though when I've accessed a site out of hours, it's been a free site. The only sites I can think of that I'd have any interest in visiting out of hours that are actually paid sites... well, they're all EH, and I'm an EH member anyway.

I've done such a thing - posted cash through letterboxes at heritage sites when visiting after dark. I felt it was only right.