My Dad is 63 and has been window cleaning for 30 years. He can still outwork most of his young subbies.
A friend of the family who died a few years back, window cleaned from leaving school on and off until his death at the age of 80. This was all done traditional and he carried on after the age of 70 - just one day a week as he could earn more in that one day than the rest of his pensions. Interesting as well is that he was a third generation window cleaner (Grandfather and Father both were window cleaners in Plymouth).