WELL IT'S TIME TO GET BACK ON TOPIC!  The Golden Rule for oil pressure is 10 psi for every 1000 rpm, and our oil pumps are sized to do it. Once that pressure is produced ,pressure fails to be a factor. The problem is OIL ,There is no oil on the face of the earth that provides proper lubrication at cold startup! While it's true that your oil thickens as it reaches temperature ,it's also true that it thickens when it gets cold, (can't start your bike on a really cold day? it's not because your coolant or your gas froze)and cold oil doesn't flow as readily through the small passages in your motor. The fact is you have fuel, but the oil flow either doesn't seal the rings or the drag from the cold oil puts more load on the battery( due to the oil pump or the starter having to work harder )and slows cranking speed,it affects compression ,and draws more amps from the battery which may drop voltage low (causing spark failure) so that it doesn't start.Cold oil doesn't produce as thick a film layer between moving parts until it warns. If your bike is in Florida on a 75 degree day it still has to heat the oil nearly 200 degrees before the motor is at full operating temperature and during this time is when the wear occurs .But if you heated the oil ,on a cold day, the bike would start and you might not even have to use the choke.preoilers are probably a waste of money,your oil pump is gear driven,which means it's a positive displacement pump,when the pump stops flow stops ,and shouldn't return to the oil sump ,(your pump doesn't run backward)oil in the passages stays there ,oil can drip off the piston and cylinder ,but the cam lobes are setting in a "tub " of oil,and this is where we fear the most damage.

I don't know what psi we need at the top end, but along the lines of what Dave said...

2-stroke lower end bearings (main, lower and upper rod) are lubed with a blast of pre-mix every other stroke.  That mixture is pressurized for a very brief instant before the intake ports are exposed to bring it into the combustion chamber.  2-strokes run roller bearings at high RPMs with very little lubrication.

Our real concern is the cam bearings. Carry on.  

The source of my oil pressure golden rule was in fact car based ,(my bad),but no matter what our oil pressure is ,the rest of what I said about oil flow is none the less true.