A Stupid "Sleep" Mode Question

Hi E1,

I know this is a stupid question, but this is something I have been wondering about for some time now.

I have my screen saver set for 10 min and since I now understand that on laptops the screen is lit by

some type of light bulbs I set the screen to turn off in 15 min. I have the "SLEEP" mode set to 2 hours.

I set the sleep to 2 hours because and this is my question, if I have something running like say

disk defrag, or downloading files or pictures or something from the web or backing up to or from my external hard drive, will the sleep mode detect that something is running in the background and delay putting the computer in sleep mode till it is finished? Or will it just automatically go into sleep mode and **poof** my download or defrag or backup is stopped and I have to start all over again? Also does having the screen turn on and off a lot do more ware and tear on the screen and bulbs then just maybe setting it to like 30 min is better?

Thank You

Rick