Oscar: concerning your statement: "As for intermediate readings, none of those are any good till you recalibrate. I do the same thing but the major use is when I mess up and have to back up the same day. Front flat and your day is over."
If you do not have a flat, you could stop measuring at any properly identified and recorded spot on the course, re-calibrate, record any adjustment to the point, then start at this point on the next day after pre-cal.
I may have been lucky with never experiencing a flat in my 30+ years of measuring. Solid tires are looking better to me the more we discuss this.