I'm the only person I've encountered that naturally runs on a 25 hour clock. I get the same amount of sleep per day (~8 hours) but I follow it with 17 hours of wakefulness so my clock moves forward by an hour every day. To my knowledge there are no adverse health effects, but it's certainly out of the ordinary. I often wonder if more people are like me since sleep problems are so common, but they cannot follow their…
Once I experienced the pain of needing to wake up for a small child, I was forced out of my historical sleep pattern. Fortunately I, like my parents, need less and less sleep as I get older, so 24 hours with an early rising child is more tolerable now than when I initially experienced it.