I agree with Hammy with waiting until you have issues showing up. Unless you just want to do it for understanding better the chemistry that goes on. If you are using hydro, you will have constant change in the solution because of the chemicals that get removed by the plants with each watering/feeding that happens, change the chemical balance that gives the pH. Also, the aeration has a chemical effect as well because you are dissolving chems from the air into the water.
If you are using a reservoir that feeds the flood and drain system, and the solution runoff goes right back into the reservoir(aka rez) then you only need to check the rez every couple days (once you get used to doing it). If it is a new thing then you should check it everyday until you get used to seeing how it reacts and changes over several days. But once you get that understanding of what to expect, you will check it less and less until you have established a schedule.
You don't necessarily want to adjust the pH every day to keep it close to 5.8, you want to let it drift from one end of the allowable spectrum to the other. This spectrum of pH will be different for some strains and certain nutrient brands. For me, using AN's Jungle Juice, I have to set my pH at 6.0-6.2 and allow it to drift down as the plants take in the nutrients. When it reaches 4.5-4.1 I will adjust it back up to 6.0-6.2. Some systems/nutrient brands/plant strains will not like that I go so far down. I allow it in my system because I am used to how my system/nutrients/strains react. I also don't allow the pH to sit very low or very high for more than a day before readjusting. I would say the best rule of thumb is to stay within the 5.2-6.0 range of drift.