On Sleep and Jet Lag

Last week, after returning from Japan, I had such a hard time falling asleep that I'd shift into a 48-hour day pattern, where I was essentially only sleeping once every two nights, but this week, that trend seems to have reversed itself, forcing me to sleep 12 hours a day. I thought about trying to maintain the 48-hour day cycle, but after seeing that this lack of sleep made me more susceptible to colds, I've decided to shift back to the normal 24-hour day. It's probably better for my health anyway, but I keep thinking that it would have been interesting to have those additional 8 hours of awake time.
Recent sleep research has shown that 8 hours of sleep is a myth, and that the amount necessary varies from individual to individual. I find my natural sleep space to be about 6 hours, which is likely why I'm sleeping 12 hours to catch up for the 6 that I missed earlier. The sleep deficit seems like a real enough effect.
I need to readjust my internal clock -- I'm so used to getting up at 6am that getting up at noon makes me feel as if I've lost most of the day. One day last week, I woke up at 3pm, and I really did lose that day completely.