I blow my system out every fall with a standard air compressor. "Up North" we stay away from PVC and stick with only poly pipe as it is much more forgiving with freezing. I know some do nothing to winterize their drip systems other than empty the filter housings and have never had a problem.
Every Spring I spend more time fixing rodent damage than frost damage. Mice really like the smaller rubber or vinyl "spaghetti tubing".
I also like to bleach or use oxyclean to flush out my systems every year to remove built up organics. (no, it does not hurt the trees)
