It can be a never ending spiral...
I have a 1972 Raleigh Superbe, it has been upgraded from a 3 speed to a 4 speed, changed from steel rims to alloy, galvanized spokes to stainless steel, incandescent lights to led....and I am sure I will find something else that needs attention shortly.
Bad part is I have about 10 bikes that I ride regularly
Aaron