Over on another forum, a correspondent posted that a professional should always purchase the top-ot-the-line equipment for "future proofing." The specific issue in that conversation was whether a professional photographer should purchase a Canon EOS R today rather than an EOS R5. I've owned EOS R bodies for nearly two years for my retail portraiture, and I don't feel any need to upgrade to the R5.
That sounded specious to me, because my experience is that technology is too quickly evolving to do much "future proofing" by buying more capability today than you really need today. Too often, by the time you really need that capability (if you ever do), it will be cheaper and/or even better by then.
Most significantly, a professional has more boats in the upgrade cash flow to consider than the camera body: Lenses, lighting, insurance, marketing costs, studio costs, et cetera.
My considerations for upgrading anything is: Will this save me more money or make me more money? I'm photographing people who are sitting relatively still at f/5.6 or smaller apertures, tethered to a computer, nearly 100% of the time. I can't see that replacing my EOS R camera bodies with EOS R5 camera bodies would save money or earn more money in what I do.

