Why mess so much with your sleep cycles? If you look at the long lives of souther mediterraneans you don't see any of this stuff. Instead: good diet, don't overwork, big naps.
In the Mediterranean especially were my Mum grew up in Italy, all the farmers, who live long lives took naps in the afternoon. This is a common practice all over the world
It is a more common occurrence in warmer climates (mexico and the siesta) and where the people undergo physical labor for work (such as farming).
No offense to the good people of the southern Mediterranean (I lived in Sicily for years), I'd like to accomplish more with my life than that. Not saying it's better or worse, just that it's my preference.
Sleep cycles are already messed up -- so this is a good way to make the best of a bad situation.