I use the plug O-rings as my guide. Rub your thumb across the O-ring. If nothing rubs off, the rings are good. Naturally, if a poppet valve gives me trouble, I'll rebuild then.
Otherwise I just scrub them out and sanitize.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk