Using a PH monitor

I'm getting ready to get a Pinpoint PH monitor, but have a couple of general questions.
1) The Pinpoint PH monitor is guaranteed for 2 years.  What has been your experience?  Do they generally last longer?
2) The documentation says that the probe lasts about 18 months.  Do you replace your probe that frequently?  Or do they generally last longer?
3) Calibration - documentation says to calibrate every month.  How often do you calibrate?
Thanks!!

 

I dont know abought the probes but i hope their ph meters are better than their wireless thermometers. After owning the thermometer i will never own a pinpoint product again. It was the biggest waste of money i have spent on my tank. Just my two sense on their products.