It took me a few hundred crossings before I figured out how to use a sleep cycle app. So I give it a 30 minute window to wake up in, and the app fires off the alarm when you're coming out of deep sleep and into light. Made me feel a lot better off the nooner and still easily able to sleep 7 on the local clock that night. But I was also sightseeing and socializing and working out, so I didn't want to sleep until 9pm. That being said, I didn't realize how exhausted I was all summer until I upgraded to the narrowbody life. Narrowbody don't just mean the airframe either. Ieat healthier, work out more, sleep better.... international flying will kill you eventually, unless you're in that 5% who seem to thrive on it physically.