I rotate through my vacs -- new and vintage -- as I enjoy using each one. There isn't a specific vacuum I use every day, though lately I am really enjoying my Dual Sanitronic 50 with its new HEPA bag conversion and Mini Emptor and tend to use it a bit more often than my other vintage vacs (1974 JCPenney Hoover convertible, 1984 Royal 880, 1988 Royal 884 and a 1988 Kirby Heritage II Legend) along with my modern Sanitare SC886 and Kirby Avalir (I have no desire to use my wife's Dyson Animal 2, -- it's there because she doesn't like using 1920's technology, as she puts it, lol).
My Kirby D50 practically a brand new vacuum -- when I restored it last summer, I installed brand new front and rear bearings, motor brushes, a brushroll, new trim and wheels, a new Amodel fan (not to worry, the fan installed in it was not metal, but Lexan, otherwise I would've kept the metal fan) and a new aftermarket bag on it, which was recently taken to a tailor to have a zippered back added to it to facilitate a disposable bag. The HEPA conversion has made it comparable to a modern machine -- yet it's the oldest in my collection so far (something like a Kirby Model C or 505 with a HEPA conversion would be REALLY cool!).
As long as you are maintaining your machine(s), are confident in being able to track down and obtain critical parts should it need service down the road and are confident in either finding a vacuum shop willing and able to service your specific machine or doing the repairs yourself, I don't see why you couldn't use it daily or semi-frequently. There are exceptions to the rule, however -- you probably would want to avoid using something like a Hamilton Beach metal upright on a daily basis as parts are surely unobtanium since H-B hasn't been in that business for decades.