This is what I suspected. The need to use the "drag brake" to keep cadence under control seems to get more pressing when your doing more miles too -- to keep from using up your legs in the downhills.
Another question then: do you both (or all if anyone else wants to relate) use standard drop-type brake levers? I don't know that I could get by in the city without my cyclocross lever. It works from all hand positions except in the drops, and I'm rarely in the drops while training in town. I was thinking of just adding a second lever of the same type. I worry that the smaller lever might be fatiguing on really long stuff, though I haven't had much problem with that on my longer rides at this point.