what is now more worrying are comments from owners who suggest that these bikes are not practical for a longer commute
Ah, well, some people can't seem to ride slower, genuinely, even when they're on a roadster
and some roadster owners really do regard it as a short-range bike... but hey, I'm mostly in Norfolk and everything's a long way apart out here. The bike's fine over distance. It's not as fast as a road bike but I think it's more comfortable.
As well as it being my go-to utility bike, I've ridden the Dutchie Dapper on various long rides and I think one century... and the bath after the century was mainly to soothe the muscles, not because I got sweaty. I almost always ride in street clothes (usually shirt, chinos and deck shoes - add jumper, jacket and/or more watertight shoes in winter), although only formal when cycling to certain types of work site. I would leave the jacket at work (or find a way to carry it neatly) and wear a more outdoorsy jacket for the ride.
I think it depends on the route and it might be hard to know for sure until you try. Where one tends to pay a penalty with heavier bikes with wide-spaced gears is in speeding up again after slowing for junctions, lights or climbs. Once it's ticking along in top (literally, in the case of three-speed bikes) then it's not a difficult task to just keep it cruising. You're sensible to plan on a 10mph average - on some London routes, I've been as slow as 6mph because of all the flipping lights.
If you want to hedge bets and go for a lightweight roadster, I really like the look of
https://www.flyingdutchman.bike/our-bikes/gazelle-vanstael-men/ - but me, mostly riding in the flatlands, I value the Dapper's stupidly-sturdy rear rack more.
