Its really personal preference. If you have your pi overclocked and leave it running all the time it may decrease its lifetime, you can also look into extra hardware like the mausberry switch or the control block and incorporate an on and off button which will preserve the life of your microusb port from being handled so often. Sometimes I’ll leave it on for a few days other times I’ll unplug it. I have 3 or 4 raspberry pi’s I use semi frequently and I’ve had them for about 6 months and have never had any issue with any of them.
Reply To: Leave on or turn off?? That is the question……..