I like Amanda MacAskill's piece on sleeping in. Amanda argues very sensibly that while we think life is the kind of good where it's better to have more of it, we don't measure the relevant quantity by subtracting the date of birth from the date of death; the value in life comes from experiencing it. So ceteris paribus, if you spend more of your life asleep, you're missing out on some of what's good about life. This seems completely right. (Whether Amanda's advice to sleep less is good depends on the degree to which the quality of waking life would be degraded, which of course will vary between individuals.)
I have wondered for a little while, however, about a further development of a point like this. If it is the experience of life that is valuable, such that more of the experience is better than less, even if the biological lifespan is the same, it seems to me that there's also a case to be made that it's better to have more of the experience, even holding fixed the amount of time in which one is conscious. It's a familiar phenomenon that sometimes, the passage of time feels faster than at other times. If I'm sitting at home playing Dominion, I could spend eight hours and barely notice it. But if I'm taking photographs in a city I've never been to before, those eight hours feel much more full of my life.
I suspect, then, that for reasons much like the ones Amanda articulates in her piece, we have some reason not merely to sleep less, but to engage in those activities that slow perceived time down, and avoid those that speed it up. This suggests, for instance, that it might be a great idea to travel more, or that it might be a terrible idea to have children. Ceteris paribus.