Ya know Tvov, I was asking myself that same question this last week while camping on the beach in San Diego. My thought was, **** I hope I'm doing this right. I bought this little 8 cup percolator when the 1989 Black & Decker just didn't look good anymore and when I let the magic hot water out all over the sink top. That was about 10 years ago and I never figured out how long to let it perc.
To top it all off, the DW asked me last week, "how long I let it perc". All I could say to her was, "until it's done". When I don't give her the complete, and detailed scientific description on boiling water and number of holes in the strainer and, and, and..., she knows I don't have an answer and she finishes whatever she needs to do to get away from me.
So not being one to let a good problem go unanswered, I sat there for awhile and came to this conclusion. "IT DOESN"T MATTER". I've been drinking coffee made in that pot for at least 10 years and I'm still happy looking out the windshield at the forest or ocean or Joshua trees while I drink the resulting brew.
Happy travels and remember, "K.I.S.S.(keep it simple son).