I've replaced my PCV twice, don't remember what my mileage was the first time, but did it again at 183K. Here's the deal, by the time you get it out to shake it and see if it's gummed up you might as well stick a new one in. If you have owned the car since new and replaced the oil like a good boy, it's probably fine. I believe they accumulate gunk through abuse and neglect, the former of which my car has endured a lot of. Changing coolant and PS fluid more frequently than 30K seems excessive, as does gear oil and ATF if you have a slushbox.