be grateful for. We used 1" pipe for everything. Didn't switch down to a smaller size for the runs off the main line like most do and most companies recommend. We also buried the pipe deeper than they say you need to and we did 6" risers instead of 4". Everything is deeper so we don't have to blow it out in the fall. We also included release valve drains at the end of every run so the water automatically drains whenever there isn't pressure in the line. And with the 6" risers they always get up high enough to water the grass without being high enough in the ground to get hit by the mower or anything.
Our system is only 3 years old, but my sister-in-law is going on 10 years with no issues and the same setup.