What you’re doing is obviously fine. I only check pH when I brew with malts I’m not familiar with or when I try a new technique, just as a means of verification. Being able to measure pH will come in handy if you find yourself having trouble, like efficiency changes you can’t account for. But ya, if you are having success and your malt and water is not changing, you’re fine. Probably
There are other uses for a pH meter than mash though. Like detecting that your starter is active.
It’s helpful to be able to measure another parameter so you could know if and how to adjust. If you’re happy with your beers, skip it. I didn’t start measuring pH until I got a sack of acidic Pilsner malt from Beat Malz. My beers were dryer than expected and had a harsh graininess to them.
If you do buy a meter, get quality traceable buffers for calibration.
Just saw this question on another thread in equipment and software. Bru’n Water is, IME, so close that it’s probably more accurate than my ability to measure either pH or salts and acid. Go ahead and trust it as long as the results are good.
Even if you rely on a model for mash pH, it won’t give you any insight into pre and post boil pH, or any of your fermentation pH characteristics. You need a meter for that. If you don’t care about those measurements, then proceed as you have been. If you want to dial in, or monitor those variables, as well as, ensure that your predicted mash pH is correct, then you need a meter. Stevie’s example of the acidic best malz lots is a great example of where an assumption based prediction model breaks down vs actual measurement.
Bru’nwater is a good predictive tool. Predictive tools like Bru’nwater rely on input data. If the data entered don’t match the actual physical parameter, the model’s out put will not match the measured value.