Outed!

Usually I only tire reading webpages in the same font after three or four months, but you're right, I do switch fonts whose design I'm testing in and out all the time.

That's probably why the example came to mind. But I think of it more as a personalization issue than a change-the-look-on-a-whimsy need.

As I said before (I never tire of repeating myself), we live in the browser. It ought to reflect our subtlest need.