are you using soil or going hydro, hydro I would check the PH twice a week, and change res once every 1-2 weeks, Soil I would test the PH every day, just test...
you got that backwards. Hydro will require you to check the Ph more often than soil. Soil acts as a buffer, so things are effected slower. I have always grown hydro and I would check my PH everyday. Adjusted it every 1-3 days depending on when it needed it. The faster your plant is growing, the more often you will have to adjust the PH. Also anytime the plant is consuming water and nutrients at a significantly differnt rate, the more the PH will flucuate.
i am running a rdwc system and i tend to check ph and ppm in the morning and then later on in the evening only takes a min to dip in the meters so not a big hassle once a week, normally a sunday job i check the calibration, normally everything is fine, mabe a point out, but better safe than sorry, seen enough ppl wondering about probs and it turned out to be monitor had failed on them better safe than sorry