After a man hasn't had sex with his partner for a long enough period of time, he begins to start measuring how long it will be until the next time he has sex. A combination of sex and metric.
Once I realized how long it's been since we had sex, I started collecting the sextrics to figure out if this relationship was even worth it!
I'm my own sextrician. Self taught of course. I try to figure out what makes me in the excite sexual arousal stage and stay there as much as possible. Until benefit has been reached and release or expulsion or discharge or finality of orgasms has been reached for a significant period of time.