Dan is on his computer for about an hour and a half in the morning, then another hour and a half in the evening. Dan is wondering if he should shut down his computer during the day, or leave it on and have it go into sleep mode. Leo says that modern computers handle power pretty well. He can choose in his power saving control panel a variety of different schemes, but the default should be fine. It will go into a low power mode that only uses a few watts, even less than what a light bulb would use. During the day, if he's going to use it off and on, that's what he should do.
Dan is concerned that his computer could wear out faster if its left on. He says the tower itself is warm. Leo says that when it's sleeping, it should not get warm like that. If it's in sleep mode, it is ok to leave on. Leo says that if he's away for more than a day, he'll shut it down to save power. But as far as the computer wearing out, there's actually an argument to be made that switching it on and off periodically will actually wear out the components faster than leaving them on. Leaving it on will not wear it out faster though, so Dan will be fine leaving his computer to handle power consumption on its own.