I'm still tending to use fast zoom lenses rather than primes for casual photography, which I've been defining all along as without tripod. This tends to be social events or quick shots while on the move.
For "serious" photographic expeditions I tend to use larger formats and primes, a tripod, and live-view focusing, but since this gear is based out of a vehicle I can carry more lenses so I don't follow Rorslett's rule. I might have several lenses in a single broadly similar focal length range, each lens with particular attributes, and several broad ranges of focal lengths. But there is also the option that I might go out on foot with just a few lenses selected from the overall group.
When at home, I do occasionally go out with just one prime, usually a normal or short telephoto, to challenge myself. And when recording indoor social events I like to use my A6000 with 12mm and fast 24mm lenses (maybe a fast 50mm as well), a combo which follows the rule nicely and functions quite well for this work.
My recent experience in the Sierra Nevada (see my Yosemite thread) called my assumptions and habits into question, as I ended up using my lightweight small-format zoom kit (intended for quick shots to record the trip) for serious work for hours at a time while my full-frame camera with nice primes sat almost unused. The one time I actually used the full-frame camera, perspective and framing required use of the zoom I had on hand.
The usual knocks on zooms are that they don't force discipline like primes do and the photographer ends up zooming instead of carefully choosing a perspective. I'm mindful of this and generally choose perspective before touching the zoom ring. The advantage of zooms is that one can choose both perspective and framing; being relegated to "foot zooming" means your perspective may not always be what you really want. And of course for nature photographers foot zooming often just can't be done, especially in rugged country.
Nevertheless, on that trip I ended doing a great deal of cropping in post, despite my efforts to get the shots framed well when I took them. One task I have is to go back and estimate effective focal lengths after cropping, and see what focal lengths would have worked up front if I'd done a more insightful job of composition in the field.
Another factor is that my DX shooting tends towards zooms due to a shortage of good autofocus primes in the wider focal lengths, and awkward focal lengths for autofocus primes beyond normal. Maybe I'm trying too hard to not waste pixels, by seldom trying manual focus when I'm not using a tripod. I am looking forward to eventually having a Df or Df2 and going out with manual focus primes to do what I used to do a long time ago.
All that said, my photography is in flux. The past few years have consisted of trying to break up decades-old lazy patterns and relearn the craft. My assumptions and concepts of how I go about photography have been changing and will change some more. Thus, I'm not at any sort of end point or even a medium-term equilibrium. My impending retirement will bring increased opportunities to try out different gear that I already own and challenge myself in new ways. I'm confident this will include more work with primes.
