I have tried that technique for a few years on my boat(s) . . . it took a looong time . . . 40 minutes might be generous. I used a shop vac and a 5 gallon homer bucket w/ sealed top. My homer bucket looked like a crinkled mess after each oil extraction.
It takes quite a bit of vacuum to pull the oil up out of a full-sized engine (V8 / V6) vs. a lawn mover. . . . assuming that you are using the dipstick tube to extract the oil. In my experience, shop vacs can only get about 3 psi of vacuum, and that does not seem to be quite enough to pull the oil up the dipstick & through the tube at any reasonable rate of speed. Maybe a vacuum pump would be better
In the end, I found that the hand pump does the trick in about 10 minutes.
I think if you can get a solid/rigid container for the oil/vacuum . . . something like a small beer keg - empty it first
- that might be better. A rigid container + a vacuum pump would be ideal. I would NOT use a glass container though . . . ( boom !!! )
I do like the idea for lawn mowers, snow blowers, and other small engines