I'm unable to leave any bike alone.
I tried with my 1977 Fuji S-10S, which I vowed would remain "stock". It looked so clean and rode admirably for what it was. But...it needed fenders. Okay. And clipless pedals to go with my riding shoes. Uh Huh.
Not a long while later, I thought that bar end shifters would be better than the downtube PowerShifters. At least the new ones were "period correct" SunTours. Of course, why not add a rack - center mound Blackburn for authenticity, but no longer
stock.
Then I thought, if it had a smaller inner chainring, I'd get just a bit better climbing ability for what was now evolving into a utility bike. Swapped a Sugino 39T for the standard 42T.
And so it goes...