oh
laptops are designed in thought that they are often switched on and off, whereas desktop computers are designed in the thought of having them on all the time. thats what i have heard that the hard disks are optimized accordingly. i would say there is not much difference, but i would say a desktop running all the time the hard disk may lasts 20% longer and maybe a lap top running all the time may last 5 to 10% less than if not on all the time, those numbers are only guesses, intuitive estimates,
i think it does not make that much of a difference,
and i do have a lappy and it is on and logged in all the time....
although mine goes in hibernate mode after time, i would think yours too, and that would be already would save the hard disk and resulting it to last long, (which is practically as switching it off)