I personally run my mac 24/7. I have a program that I run throughout the day and part of the night, but I have my laptop set where it doesn't go to sleep. I've only been doing this for maybe 3 or 4 months. Prior to that I would shut it down semi-regularly. I've noticed that for me my laptop has been running more smoothly keeping it up all the time, but that may just be coincidence. c: