Ab,

I have used my plastic in-line pressure regulators for 10 years and still going for my two drip systems. Other components of my drip system haven't survived as long. I don't remember the brand name. It could be from other water pressure problems that they may be failing. Are the exposed to the air or are they buried? What is your system's static water pressure? Aloha

I've found the sun/air/heat is brutal on the plastic, so this year I boxed in the filter and regulator with a lid, so the sun doesn't hit them.

This particular pressure regulator lasted 2 months.

Static pressure is about 95 PSI, but since the regulator is after the shutoff valve, it's only subjected to this pressure about 8 hours per week.

Ab,

95 psi is very high for an irrigation system in general and high pressure is prone to more severe water-hammer impacts. These devices are designed for more normal operating pressure reduction say from 55 psi to 25 psi. The higher pressure may be causing your auto valves to close faster thus sending a shock wave to the constriction point(pressure regulator) and slamming it. You might think of getting a more heavy duty pressure regulator like one your house uses to 50 psi then the in-line plastic ones after that for the drip side of your system. JMHO Aloha