Yup. Every 30 days at the very least for a quality meter like a Bluelab.
I calibrate mine every two weeks.
Cheaper meters I would do at least once a week or better yet, get a better meter..
I'm on the cheaper side got my 7 and 4 solution now it once a week. I don't trust it too many problems I'll probably invest in a blue lab
what do you guys recommend
Here is a short video on how to calibrate a Bluelab PH pen meter.
https://www.youtube.com/watch?v=EYL62M9Y9CQ
Just a remark about the video.
It's best to keep the probe into a shotglass submerged into the kcl storage liquid instead off adding a few drops in the cap. I find that with just a few drops in the cap the probe isn't sufficiently protected.
Don't even for a single day let the probe dry out. It needs to be kept wet into the kcl storage liquid.
The presence of concentrated KCl solution keeps the ionic conductivity of the glass membrane in good condition. The conductivities of K+ and Cl- ions are the same.
KCl is not a buffer solution, and is never used to calibrate the pH electrode, but is used to keep it working properly - it keeps the glass full of ions.