I know this is an old thread but the beauty of the internet is you can continue to expand upon things. I suppose like some of the other people here, I don't understand the whole premise of this thread.
"I kind of move a lot and i can dissemble and assemble computer parts within 3 mins (yes i can do that in lightening speed). Case make it bulky and difficult to move. "
I'm with another poster in thinking that this is a ridiculous statement. The OP is stating that it is easier to take every component off of his board, unplug his drives, disconnect the PSU, etc. instead of just unplugging the PSU, monitor, and keyboard / mouse (which he'd have to do anyway) and then carrying all of those components (somehow... plastic bag? box? I wouldn't trust those things banging around in something) instead of just carrying a case, many of which have handles.
Further, you can not be 100% certain that you will never spill anything on it or that nobody else will ever mess with it. At least a case offers SOME protection. I have a > $3000 desktop and there's no way in hell I'm leaving that investment to random chance. Also as someone else said, a case improves airflow and increases the amount of cooling hardware you can install. Aiming a box fan at your exposed motherboard is not the same as having a cold air intake and hot air exhaust to dissipate heat. I read that after 3 years your rig is still doing fine, that's great. I'm still not willing to risk melting my CPU in order to make some arbitrary point.
Just my 2 cents for anyone else who stumbles across this thread 7 years later like I did. Hardware runs hotter than it did back then and decent cases have become even cheaper. Don't risk thousands of dollars just because you like looking like the guy from Pi. There are transparent cases.