I can't remember the last time I replaced brake pads... which probably means it was about a year (and 3000 miles) ago. I usually switch to Kool Stop salmon-colored pads once the OEM pads wear out. The two things I've found that cause pads to wear quickly are: 1) dragging the brakes continuously during a descent, and 2) riding in the rain. I was surprised by that last one! Seems like a lot more dirt/mud/gunk gets stuck to the rims when the roads are wet and forcing the brake pads to scrape it away accelerates wear. YMMV.