The last time my dd and I flew together, I lucked out and got precheck. I got through the security line about 5 mins before she did....that was at MCO.
But, there was the time my dh got lucky and had precheck in Boston. I didn't get lucky that time. However, I beat him by 4-5 mins. Go figure. I think that with passengers being sent to that precheck line, but having no clue what to do, it can make that line take longer than it should.
I never buy just more speed. I do sometimes buy extra legroom seats, will also gets me in the more speed line.