When I bought my car in 1987, the original blades were already gone, replaced with black ones. It never occurred to me to grab some originals at the scrapyard back then. It always has had the ugly black ones and with the adapters, they stick out so darn far from the glass (the arms I mean). I had put the same thing back on the car after the complete bare shell rebuild and suddenly, they looked horrible and the search was on. Settled for the Cadillac blades. Like I said, all that work to find blades for something I'll never need to use (hopefully). Also rebuilt the wiper motor and put new pivots and linkages on. At least it all looks nice and purty, lol!
The only time I'd replace the entire thing is if the originals get worn out and loose. On vehicles made in the past 25 years or so though, the inserts are generally not replaceable anyways. My '96 Dakota is like that so the originals are LONG gone. The '08 Mustang uses beam style so there is no actual "blade" to begin with.