I'm pretty familiar with the DC suburbs and between normal daytime traffic(not even considering morning or afternoon rush hour), traffic lights, and the time to get to a main road from you community(very slow speed limits) a half hour wouldn't surprise me at all and 45 minutes is very possible.
I am in southern California, and perhaps the suburbs here are more concentrated than suburbs elsewhere. I have three pharmacies, three grocery stores, and a Walmart all within 10 minutes. It does require taking a car, though.
45 minutes round-trip: 20 minutes there, 20 minutes back, 5 minutes at the store. With only moderate traffic, of course, rush hour (which in the DC suburbs extends from noon to 9 pm) can easily extend this to an hour.
Compare to Chicago where running out of contact solution means taking the elevator down 28 floors to the 7-11 in my building.
And I don't know about So-Cal, but Nor-Cal "suburbs" are far denser than in DC. People call Silicon Valley a bunch of suburbs, but as far as I can tell its a series of small urban centers connected by a highway.
