Hi, I have just joined this forum and have 40 years of experience in building maintaining and repairing audio equipment and I was naturally interested in this thread. However after reading some posts I thought for a moment I was in the good housekeeping forum with all the talk of polishes and cleaners etc. I feel that keeping loudspeakers in good condition means maintaining their ability to produce accurate undistorted sound. So with that in mind, some suggestions: rotate bass drivers 180 degrees to help reduce cone sag and therefore coil rub and tighten all bolts to stop any rattles. While the driver is out put a couple of silica-gel dehumidifier packets inside or If your speakers are ported, drop them in through the port (I have had to replace many drivers suffering from oxidised coils due to damp or humidity). While you're at it check the gaskets aren’t so compressed that they no longer seal. Clean the driver terminals if they are the push-on type and make sure they are tight. If the drivers have foam surrounds, check for disintegration. Unfortunately, there’s not much can be done to reverse this but because exposure to air is the cause, their life can be extended by coating with non acidic rubber cement if it’s applied before disintegration happens. As far as cosmetics are concerned use whatever works, just don’t stick them in the shower. - regards Macmack.