Vac advice- how much and what hg is best?

What is the best way to vac?

I currently bring my vac down in approximately 5 hg increments until oil is nice and flat at full vac. I was taught to that keeping the vac running the whole time was the best way to go for maximum extraction of residual solvents. To increase the purge I was taught to release vac and flip oil 2-4 times,

I read and see where many people don't run their vac the whole time and I can't help but wonder which method is the best for quality and safety. I have a pretty powerful refrigeration vac pump that pulls something like 15cfm and I'm not sure how many hg as it pegs out needle past -30 hg.

I do run the vacuum the whole time, just not as long as some. I typically keep the vacuum pressure above 10,000 microns, or about 29.5" Hg, using the vacuum control, or by bleeding a small amount of N2 through the back fill port..

Starting with cotton candy, I am typically under 10% of FDA Class III residual solvent standards in around 4 hours.