I try to do three samples on each patch yearly. that's three on the upper, three on the middle, and three on the lower [all both right and left side] for a total or six samples in each patch, three times a year. NC does not charge me for this as song as i don't submit samples in peak season. If it was not free, It's unlikely that i'd utilize it so much.
doing it in this way, I can calibrate my soils addendum of ONLY organic materials, like gypsum and the seaweed spray i use. I am keeping to the organics addendums and documenting all of that stuff so our product can eventually get a Bio-organics certfication. MOre on that later...
Agreed on nor lowering your pH yet. I understand that it's easier to lower it however once lowered is difficult to bring it back in case you over shoot. I have found that raising the pH is tricky as well.
High levels of Ca are desirable, as far as I can tell from readings and postings here. I have the opposite problem, and have to raise my Ca, hence the regular addition of gypsum on my patches.