Thanks for the reassurance, everyone.
(I need to clarify that 25 mph is for a 1 mile burst, not a sustained cruise - on my commute bike carrying my backpack and my 50 years I'm not exactly TT'ing. There is a four lane road with no bike lane that I take for a little ways because it is direct. At 25 mph you are close enough to car speed that drivers treat you like a slower car - don't taligate, give you the whole lane when passing, etc - but at <20 mph you start getting a bit of questionable behavior. Strong incentive to speed up.)