Anytime with my girlfriend. When we bring home a guy though, I let Raquel go to town on him at first and then I wake him up later for a fuck in the middle of the night. If she's asleep I love making him cum on her or in her mouth (and so does she). He also usually wakes up to a blowjob from both of us.
In the morning at the weekend when I haven't got to go to work. I like just laying there with my partner, we keep dozing off, waking up, cuddling up and building our closeness up before eventually making love for hours. We'll then get up and go out for a meal or brunch.