It's actually the other way around. High manifold vacuum conditions are when you'll collect the most oil through the catch can, and this will occur mostly under part throttle driving. So driving around normally on the street or on cruise is when these are needed the most.Early signs are that I am getting 7ml per 1000 miles
I think you need to balance these kind of questions to car usage though - easy driving v track time etc ...
As a guide mine is road usage, but I like to play and it isn't used for commuting or motorways much, I also like to let it rev.
If mpg can be used as a metric to judge usage, I'm averaging mid 12’s to mid 14’s (and that's a 'large' UK gallon for anyone stateside reading this), I don't doubt that if I was mostly cruising at low revs and highway miles the can would catch a lot less oil