Hanna Instruments has always targeted this market with reasonable priced/reasonable performance pH monitoring products.
Regardless of claims, you should
check your calibration weekly, choose a standard or reference solution that is close to your measuring pH (of interest), make sure this is used & stored correctly (ie dispense a small volume to check your probe, then discard; never place the electrode directly into your reference or calibration standard bottles, you can purchase single use envelopes of references/standards).
It's recommended to use a reference solution that is NOT one of your calibration points, eg if using pH 7 & pH 10 as calibration solutions, choose a pH 8 as your reference check.
Actual calibration may only need to be done occasionally.
Depending on what you do with the sensor membrane & how this impacts the internal reference, any pH pen/probe can last a good (or short) while.
The sensor part of a pH monitor can range in cost from a few dollars to hundreds of dollars, same goes for the electronic component - those sold for the aquarium trade are a dull, stolid lot & hold up well to abuse
- in exchange the pH measured is around 6.2 (precision & accuracy are the compromise, most of these sort work well in harder water, not so well in soft water ... add 100mM NaCl or KCl & they perform to specification)
(note that electronic calibration does not check pH sensor performance, it's meant as a back up check or refinement to solution calibration)