[nerb]

> don't involve spending an appreciable fraction of your day shopping.

if you're concerned about how your time is spent, i think you're missing a fundamental piece of the puzzle: how much time you spend driving. you could end up saving an enormous amount of time while still going out to shop more if you cut out driving and reduce the scope of your trips.

[bluGill]

Not really. People tend to have tolerance levels for commute type activities, so while cars enable going farther in the same amount of time, the time budget doesn't change. If they have a walkable city they are likely to find reason to go to a farther away store if it is still in the time budget.