Windows 7 - Computer Sleep question/suggestion?

I have heard many side of the debate about weither or not to sleep or Hibernate a PC, or shut down or leaving it powered on.

Here are my two setups, let me know what you think should be best. I want to try and conserve power, while not impacting my computer usage that much (if at all)

Both PC's are running Windows 7

Desktop- I leave this one running 24/7. I kinda make it my personal "server", and i use Windows Live Mesh to snyc my PC's together. I do open it up 3-4 times a year and blow out dust with compressed air, so that dust does not build up. Ive been doing this since i got my first PC in 2002, and never had a hardware failure (except one failed Hdd). I have a Flat Panel LCD monitor, which i turn off. Would it be better to let the LCD "sleep" too?

Laptop-I power down this when im not using it. My main consern is about putting it into sleep mode and sticking in a Neoprene sleve, and carrying it around in my backpack (im a college student). Would a sleeve or a backback restrict airflow, and possible overheat? or would a computer be more prone to damage while powered on? (sleep or full power?)
The laptop i am also tired of having to boot it up before my classes start. is it ok to leave a laptop on 24/7? Im thinking of getting an external cooler and fan, and leaving in on there while im at home/and or charging the battery

i see no problem with sleep for the portable/laptop if all devices come back healthy. in the past i had issues after one of the Windows 7 updates, but since cleared it up by setting each parameter individually. have you considered an ssd in that notebook? you can get the boot time down to 20-30 seconds and save some battery. I use a crucial c300 60gb one and it has been flawless so far, and inexpensive if you shop it. some vendor or other is always running special price on it. put bulky storage in a usb drive