I've settled on having dedicated pipes for VAs, VA/burley flakes, English, Balkan, Penzance, and aromatics. And I have 6-10 pipes in each category, allowing me to smoke a single pipe (but multiple bowls) each day and still stick with a particular style, if that's what I'm feeling like. This guarantees that each pipe gets at least a one-week rest between smoking days. In reality, though, some pipes may sit for months without being smoked. (For instance, I've reduced my Penzance consumption a bit in order to conserve my cellared tins.)
Most days, I stick with a single tobacco style and a single pipe, smoking 3-5 bowls in that pipe, unless a blend just isn't hitting the right note on that particular day.
While this is the pattern I've adopted, I'll say that when I started out, I smoked anything and everything in a single pipe -- and didn't have a clue about "resting" a pipe (or much of anything else!). And that pipe is still with me today -- and still smoking wonderfully after 33 years.
Bob