Set them when you have the time. I set my eggs in the evening after dinner. Setting them in the morning can be chaotic if you have kids to get off to school and then have to head off to work. At least for me, it can be.
I turn on the bator a few days before to make sure it is holding steady and the turner is working.
You should turn the bator on at least 1 to 2 days before you set the eggs so you can get all the gliches worked out and the temp set. You should only let eggs sit for 7 days or less to ensure freshness, and make sure you turn them at least three times a day if you dont have an egg turner. It really doesnt matter when you set them i guess. If they end up hatching during the night it doesnt matter cuz they should stay in there until fully dry and they can go without food for 2 days, hope this helps.