We have a pile of toothbrushes sitting on our bathroom counter. We seem to alternate among them and as they pile up, I realize it's time to toss the whole lot and start fresh. It's healthy to do this every once in a while. But how often? Every three to four months. Why? Because frayed bristles -- we've got plenty of these -- don't clean well and leave teeth ripe for tooth decay.

Got an old toothbrush? Toss it now. Toss these things too.

Vitamins. After two years, give your vitamins the boot. Experts say they can technically sit for three years but since you have no idea how long they sat on store shelves, two years is a good time frame. They won't hurt you if you take them years and years later. They just won't work.

Air Conditioner. Don't toss it until it dies. Unless it's a definite goner, a little maintenance should keep it running smoothly. Do check your filter every six months, though, and make sure it's cleaned or replaced so the air you breath is of the healthiest quality possible.

Cutting Board. The decision to replace one of these should be based on when you think it looks too beat up. How you sanitize the board, not its age, is what kills bugs such as E. coli and Salmonella. No matter how deep the grooves or cracks in your board, it's safe if sanitized after each use. Here's how to do it right: Wash board with detergent and hot water, then rinse and flood with a solution of one part full strength white vinegar and four parts water, let sit for five minutes, rinse with clean water, pat dry with clean towel, and air dry.

For more when-to-toss tips, check out these slides.