The "rocker arm" problem that the Pacifica has is actually a lifter issue. There is no way to completely avoid it, but using a thinner oil than recommended, like a 5W-30, will help in getting oil to the lifters quicker on cold start-up. You can also try switching to a high-grade full-synthetic -- like Mobil1.
There is no prescribed replacement period for the knock sensor. Just keep an eye out for a check engine light bearing a P0325 code, which is the knock sensor circuit code.