Thanks, everyone. It sounds like I'm on the right track for the things I use 35mm for. I don't use autofocus, auto exposure, or metering modes other than spot, so those aren't relevant, but I do wonder about things like dust on the pellicle mirror, which I can just experiment with and see how it goes, and heck, if I decide I also need a 1V later, that's not out of the question.
"EOS bird lens"--well, my bird lens of several years now has been an FD 600/4.5, and I have that rare original Canon FD-EOS converter, so I can continue to use it on an EOS camera. The optics in the converter make it a 1.2X adapter as well, and since I often use that lens with a FD 1.4X-a adapter anyway for bird photography, that's just fine. It's been a good lens, and being manual focus it is lighter than an EOS lens of similar dimensions, and as I say, I'm not interested in autofocus, even for birds (except maybe for flight shots), but the optics of the newer lenses really are better, so maybe one of these days I'll think about replacing it with an EOS bird lens.
In a typical good bird photo op, the bird is about 12-15 feet away and may require a short extension tube, and I never "spray and pray," so I'm always trying to get as many good single shots in as I can before the bird flies away. And if I get 20 shots off in a few minutes and I think as I'm shooting that 15 were good, I know that the bird moves faster than the camera and I do, and there are things I don't see during the mirror blackout, however brief that is, and it might move its head so I lose the catchlight or change the composition, so when I see the slides, I expect that maybe 5 or 6 of the 15 shots I thought were good are in fact really good, and that's why a 6ms lag time, as opposed to 55ms is interesting to me.