Steve C
I said when I spent every weekend, it seemed to help, that means going to the Sierras every weekend for months at a time.
#5 refers to spending one weekend only at altitude on the weekend prior.
#4 refers to a considerable amount of time 2 out of 7 days for a long time, not just one weekend. Though not continuous, I was spending maybe 20% of my time at the same altitude range. This is enough time for the body to start actual red blood cell production.
You are welcome to get a copy of Mountaineering medicine and read it for your self, or to actually do some online research of your own.
Also #4 refers to adapting to altitude, #7 refers to not getting kicked as badly.
Jim