Admittedly my take on this subject weighs very heavily on my 28-year absence from the sport: I tend to prefer to stay within the decade of the frame, if only to fully experience what decently top line cycling was in each era. Obviously there's a huge difference between my '71 Tour de France (Simplex/Mavic), '85 Rossin RL (SIS Dura-Ace), and my '03 Fuji Finest (9-speed Ultegra), and what I ride depends on what period I care to experience that day.

And when I do play with the setup, I usually voluntarily limit myself to treating the bike as if it was something that I'd owned for about 3-5 years and are doing the usual upgrades as better bits become available. My '69 Magneet follows that trend, SunTour Compe-V/V-GT have replaced the Valentinos and I went to Weinmann alloy rims and quick release Maillaird hubs replacing the cheap steel wheels. Both changes were normal early 70's upgrades on a late 60's bike.

Assuming I add a few more bikes to the garage, no doubt I'll be playing a little faster and looser, although having been a historical re-enactor for over 20 years, the concept of 'period correct' is very near and dear to me. And it spills over in other areas, such as cars, motorcycles, stereo equipment, etc.