Having owned many honda's, my experience has been that when the PCV finally sticks shut or open from sludge build-up, you will notice a distinctive odor eminating from under the hood, like unburned fuel or hot oil, choking exhaust fumes, etc. Then it's definitely time to change it. It's a very cheap part so you could even replace it every 20K for example, just to avoid the stink. Many dealers used to replace it, needlessly, at each oil change, but probably not any more.