The amount of time to spend in the same spot would hinge on a couple of things:
1. Your familiarity with the water at hand.
2. Your personal temperament
On new and unfamiliar waters, your "chart search" will undoubtedly yield a mile-long list of trial sites. In this situation, it's more important to touch base with all the most promising spots until you're able to distinguish a "trial site" from a "holding site".
On familiar waters however, you already know where to find bass. How you cover those honey holes will probably depend on your personal temperament. Speaking just for myself, if there's been no action for 10 or 15 minutes I'm going to change my retrieve rate or maybe my lure. That failing, I'll move to deeper water, since I always begin fishing in the shallowest cover. If there's been no contact after 10 or 15 minutes, I'm off to another holding site. But bear in mind, I'm also the type who hates to sit in traffic ;-)