Neil G.

I do, and not due to any conscious effort, or history as a bike racer, it simply seems to be the cadence that my body discovered to be the most-efficient way to cover long distances while touring. Every few months on a straight stretch of road I'll get curious and start the timer on my computer and count out strokes (computer doesn't have a cadence function), and "yup, still ~100". My wife, who learned to ride a bicycle at age 35, and thus is still such a "newbie" that she has trouble making tight right-hand turns, does 90-95rpm naturally (admittedly taking some influence from me). I know we're certainly at the high end of the curve, but I haven't felt like an extreme outlier when observing other touring cyclists.

Our cadence then explains why we have 40-30-22 cranks, and almost never use the 40t ring (I think my wife has literally never used it). So if 40t is already a bit a of a waste, anything bigger than that definitely would be! A 30t big ring "limit" and 90rpm cadence equates to ~20mph. We frequently go faster than that, regularly into the high 20s/low 30s, but that's coasting down hills, where any effort to push faster than that would be largely burned up by strong wind resistance at those speeds, would take away from our ability to enjoy the canyon we're flying down, and would be better saved to be spent more-efficiently on the inevitable uphill following that downhill.

So yeah, as someone who could get by fine with a 30t big ring, the idea of "downgrading" from a 50t to 48t sounds like a couple of empty-nesters downsizing from a 17-bedroom house to a 15-bedroom house. Like, I guess that's technically more-efficient...? Of course if you're a slow-cadence rider, the 50/48t might be useful, but then at 60rpm the 26t->34t low-gear combo becomes the useless one, as you'll be spending more energy to keep from falling over at 3.7mph than you'll be directing up the hill.

Yup, I also hit 40+ mph now and again. But that's gravity doing that for us, not our legs!

Depending on the totality of your setup, that could work, but I definitely had trouble with a 36T cassette and the M772 derailleur. It's unfortunately not a very robust combo (whereas M772 + 34T hasn't had any issues). The basic issue is that in order for the derailleur guide pulley to clear the 36t cog, the B-screw needs to be adjusted such that the Shadow derailleur design leaves a huge gap between the guide pulley and most of the middle cogs, which results in poor/non-existent shifting amongst those cogs. My solution was to "downgrade" to older Shimano derailleur technology (RD-T4000), and now the gap is much closer, and the shifting is far more robust. You can read all the gory details in this thread.