They are NOT cleanable. The tip of the actual sensor is ceramic, and is porous. Therefore, if you try to spray any sort of cleaner in there, it will make the sensor ineffective. Think of trying to clean spark plugs: no good way to do it, just replace 'em.
BTW, they're good for
at least 30k miles. You have something else going wrong if they don't last that long. Possibly oil fouling? Vacuum leak? Just throwing out some ideas.
