Having more than one vacuum means you can, if you choose, use a different vacuum when you feel like it. When you have 40+ vacuums, you're positively spoiled for choice. My normal pattern was to use a different vacuum each day, or sometimes multiple vacuums in one cleaning session for different tasks.
Of late, however, I find myself using only two vacuums in a single week...an upright for the carpets, and a cylinder for the bare floors and dusting. Here is my current weekly 'set': the Renaissance and the Epic 3500. It may or may not be a coincidence that they have more or less matching colors.
One reason for this is that my vacuum storage/display room is in a bit of a state at the moment. I really need to properly organize and display my machines, but that's another story. This room is also in the basement* of the house, so I've found its easier to carry up the two machines at the beginning of the week and leave them upstairs for the duration, or until I want to change them.
Another thing I've found is that the Style R models and the uprights are really the only machines that get used anymore. They're just too damned convenient. Once in a blue moon, I'll bust out an older model, but this is becoming rather rare. I also have decided to not get any more machines, unless they're on my wish list, and all of those are newer and useful models. My vintage collecting days are done.
At any rate, I daresay the next weekly set will be the Aerus Lux Guardian C154E and the Epic 3000, but who knows? One of my resolutions this year is to organize both my collection and its storage space. The other is to (hopefully) complete my wish list, as seen here.
*For whatever reason, the vacuum I use most in the basement is:
