I used to clean chains regularly, but I stopped. I don't have time for that nonsense, and I don't believe it actually prolongs the chain's life. The other week I snapped, though, and did a major scrub on the drivetrain of my road bike. It was so filthy it was making me crazy. But I didn't try to flush the grease out of the inside of the chain like I used to do, I think that's bad for it. Just cleaned the outer surfaces. Hopefully that will reduce the accumulation of grime on my derailleur pulley wheels and rear cassette for a little while. Looks much nicer, now.