[Cal_stir]

I have a digital aquatics ph probe that I kept submerged 24/7, I cleaned and calibrated it @ every 4 months, it worked well for about a year, I have a milwaukee ph/orp controller that I stored the ph probe and used it periodically to compare to my DA probe, I have replaced the DA probe with a pin point probe that I will keep submerged 24/7. When the DA probe failed, it started dropping slowly over a few days, I tried to calibrate it but it would not calibrate properly and shortly after calibrating it was different than the cal solution. Most manufacturers say they last 1 to 2 years and much shorter if they dry out. Double junction probes are more resistant to contamination from harsh conditions. The glass ones are refillable and are for very harsh conditions but not economical for aquarium use, I use the gel filled epoxy ones.