No reason to leave the drain plug out for two hours. It's sufficient to do it until the oils stream turns from solid to drips. Once you're down to a ten-count between drips, you're done. None of my cars have ever failed me due to oil change issues. As a matter of fact, I used to have an old 1951 chevy truck that didn't have an oil filter on it (it came with one, but it was the source of too many leaks). I just changed the oil every couple of months, regardless of driving. That truck's been running on and off for more than 20 years doing that. Never leaked, always ran. I had more issues with the carb gunking up with varnish after sitting for too long than oil issues.
No reason? Really?
Two simple yes or no questions for you:
1#. Do you think dirty oil and metallic particles are not remaining and clinging to engine parts after you quickly screw the drain plug back in?
Yes or no?
#2. Allowing engine oil to drain thoroughly does not help eliminate a good percentage of dirty oil and metallic particles?
Yes or no?