On/Off vs. Sleep Mode The new retina MacBook Pro is boot so quickly that if I don't use it for even 5 minutes it doesn't make a difference to me whether I shut the computer down or sleep it.

What is the best option for computer preservation? Will a lot of rebooting in a day will ruin the computer?
I really don't think it matters. I put my MBP to sleep all the time because I like always opening it to exactly what I had open before. There are probably plenty of arguments that you can extend its lifespan by doing something or other, but unless there's a defect or you drop it in the pool, it's going to be obsolete long before it wears out.

Additionally, on flash-based Macs (Airs and Retina MBPs) running on battery power, the default setting is to go into standby after 70 minutes of sleep. Standby is essentially hibernation - the contents of RAM are saved to flash and the machine is powered off almost completely.