<< If you turn your computer on more than a couple times a day, you may be using more electricity, assuming your monitor would be off when not in use either way. >>
Thats completely wrong. PC uses almost identical power immediately after turn on or after its been on for hours. Wear and tear? The only thing in PC that could suffer from wear and tear is hard drive and fans. Since default energy saver shuts off the hard drive after one hour, it doesn't make much difference in component life if you shut it off. Mine gets shut down three or four times a day.
It almost always gets shut down when I sleep. Its nice to sleep without the constant whirring sound.
Assuming your PC use 150W of power, lets how much energy it use and how much that equates to in power cost.
.15kW x 24hr x 30=108kWh
108kWh x ($0.1 per kilowatt hour)=$10.80 per month in power bill just for the rig itself. In many European nations, it can be over $.25/kWh and that means over $27.00 in power used by the computer.