Cog tooth wear is an overrated nonsensical urban myth created by the modern bike industry and local shops to make you purchase expensive 9, 10, and now 11 speed cassettes, more frequently than needed. We're led to believe that good steel cogs can wear out in a few thousand miles. I'd contend, that under normal conditions (not MTB mud and dirt racing), if cleaned off the bike (and the chain receives the same good care) on an annual basis, vintage freewheel cogs can last for tens of thousands of miles.



Think about your car for a moment. Even a wonderfully modern engine and drive train, which is superbly sealed against the elements and environment, is supposed to have its oil changed every 5000-10,000 miles. Therefore removing and cleaning the chain, freewheel/cassette and chainrings once a year or every 1000-2000 miles makes the most sense in order to preserve your investment, but unfortunately doesn't happen.

YMMV.