What is a reasonable pick up time for Sunday after a boarding?

Hi. What would you say is a reasonable time to ask for the client to pick up their fur baby after a weekend boarding (Friday morning drop off at 6:00 a.m. pick up at 6:00 p.m. on Sunday)? I had a client come late Sunday evening and I felt like it was a little rude on their part. Maybe just me, but I like to be able to clean up after a boarding, especially when the dog was over 100 pounds and was not potty trained like the owner said he was. Thoughts?