I started riding fixed gear bikes at 40 and am now 43... in that three years I have ridden in excess of 15000 miles fixed on a number of fixed gear bikes as what was one bike, has now become five.
I started with a mid 70's Peugeot that is presently on hooks as an accident wrecked her fork so until I replace that fork I have been forced to ride this... a 1940 CCM that was previously a coaster bike.
Poor me...
I also ride a 1955 Raleigh Lenton that came as a fixed gear, have converted two Kuwahara mtb's into fixed and fg/ss bikes, and have a 1973 Phillip's folder that is also a fixed gear.
At least half of my riding is done fixed and I have a great time doing it and at times it is the only riding I can do because of nerve damage in my lower back which makes pedalling with my right leg difficult.
I would never corrupt a frame so that it could not be restored and warn people against this and saved a Ron Cooper from becoming a "beater" fixed gear as the potential buyer did not know any better.