I still have my original PCV valve at 126,000 miles. They just don't fail like they used to when the oil was lousy and the valves would load up with sludge. Since it is near the throttle body, I often spray it out when I clean the throttle body, but I probably don't need to. It still works fine. If you can hear the valve rattle when you shake it, it doesn't need attention. It is worse to have the wrong valve than to throw away a good one. Aftermarket valves are notorious for not properly matching engineering specs.
I change my plugs every 60,000 miles.
