As I understand it, one common source of gum irritation is plaque/tartar buildup under the gum line. My dentists and hygienists have told me that "plaque" (bacteria setting up housekeeping as biofilm) tends to harden into tartar (and become more irritating as well as harder to remove) after 24 hours or so. I've also seen "48 hours" cited. I'm sure each of those numbers depends on the researchers' judgment of when plaque becomes hard enough to be called tartar, and possibly dentists'/hygienists' judgment of what it'll take to scare me into brushing more often.

For years, it didn't seem to make much difference whether I brushed once a day, twice a day, or occasionally skipped a day. My impression now is that I wasn't hitting all the right places so whether I got the other places clean, superclean, or only half clean didn't matter that much.

Trying harder to follow my dentists'/hygienists advice didn't help much. Not only were at least some of my efforts misdirected, but I came to resent what I regarded as intrusive and not very useful advice. When it came (theoretically) time to brush, I'd often be too sleepy to care. Curiously, what seems to have made the most difference for me was one hygienist's bad advice. It turned out that regular Waterpicking at maximum pressure was clearly too much, but the same procedure at about half the pressure worked quite well. In the year or so since then, both a subsequent hygienist and my periodontist have told me that my oral hygiene was "good".