Product Shelf Life:
What Are You Waiting for?

Motor oil: 5,000 to 20,000 miles (or as recommended in your owner's manual)
Many mechanics still push 3,000-mile intervals, but you can usually stretch it, say the experts at edmunds.com. Also consider using synthetic oils. Yes, they are more expensive, but they do a better job of protecting your engine from heat and wear on certain kinds of cars.

Smoke alarm: 10 years
The National Fire Protection Association recommends replacing your smoke alarms every 10 years (sooner if they don't respond properly when tested). That's because the technology is always improving. And like any device, an old one can fail. One trick to help you remember when to change it is to write the installation date on the alarm when you set it up. Or make a simple hash mark on it every time you replace the batteries, which should be annually. If you have 10 marks, it's time to go shopping.

Vitamins: 3 years (if there's no expiration date on the bottle)
The active ingredients in vitamins break down over time, causing the pills to lose their potency, according to William Obermeyer, Ph.D., vice president for research at ConsumerLab.com.

Toothbrush: 3 to 4 months
Old brushes may harbor bacteria, increasing your risk of gingivitis. Plus, frayed and splayed bristles do an inferior job of scraping plaque, say the experts at the American Dental Association. Also consider buying a new brush after you've had a cold or the flu.

Contact lens case: 3 months
You'll reduce your risk of eye infections from parasites and fungi that grow in the case.

Razor blade: 2 to 4 weeks
Gillette says five to seven uses, but if you soften your hair with hot water and lather, blades stay sharper longer, says Allan Peterkin, M.D., coauthor of The Bearded Gentleman. It also helps to hit the razor with a blast of air from your hair dryer after each use.

Pillow: 1 year
Pillow: 1 year

Mattress: 9 to 10 years
You flatten the coils over time, notes Dr. Winter. A lumpy mattress can stress your back.

Bedsheets: 1 to 2 weeks (wash)
Germs from your skin, mouth, and nose multiply on dirty sheets and can cause respiratory, gastrointestinal, skin, and eye infections, says Elizabeth Scott, Ph.D., of Simmons College. It's best to wash linens in hot water.

Gym towel: 1 use (wash)
Your towel may pick up other people's germs from the machines, the floor, the locker room, or other areas exposed to human skin, points out Scott.

Running shoes: 7 months (if you're running 10 to 19 miles a week)
Shoes lose their shock absorption and stability, putting you more at risk of knee and ankle injuries, according to the American Academy of Podiatric Sports Medicine.

Passwords: 30 to 90 days
Hacking programs can zip through 30,000 words in one second, says Kim Komando, host of the tech radio program The Kim Komando Show. For a password that's tough to crack yet still easy to remember, convert a sentence into letters and numbers. For example, turn "I want to go to Maui in 2014" into "Iw2g2M4."

Best Before When?

Food shoppers frequently believe "best before," "expires on," and "sell by" dates are one and the same. They're not. And much of the time, these dates are indicators of food quality, not safety. Here's what you need to know about the shelf life of your groceries.

Best Before and Use By:
Typically found on shelf-stable products, such as condiments and canned food, these dates refer to how long the item will remain at its best quality when unopened. If the date has passed, look, sniff, and taste the item to gauge its quality. Most items, once opened, should be tightly sealed and stored in the refrigerator. The website Stilltasty.com has a useful "Keep It or Toss It" database to help you make the final call on the shelf life of your opened and past-date foods.

Sell By:
Found on perishables, the sell-by date lets grocers know how long they can keep items on their shelves. Consumers can safely store the product at home and use the food after this time. For example, refrigerated poultry can be used up to two days past the sell-by date, and milk may still be good up to a week later.

Expires On:
Toss any food item—unopened or not—after this expiration date has passed.