Smart Money has published a guide about when to replace common household items. Here are the items they mention and the recommended replacement periods. (The complete list includes “expert” reasons for replacing each item on a particular schedule.)

  • Air filters — six months. I’ve always heard that furnace filters should be checked every month and replaced every three months. We replace ours in November and March. For more info, check out “How often should I change the furnace filter?” at bookofjoe.
  • Computers — four years. It seems silly to recommend a specific timespan for upgrading a computer. You should upgrade when your computer no longer does what you need it to do. I upgrade laptops frequently (every two years). But my desktop machine at work is nine years old and still running well.
  • Cosmetics — three months to two years.
  • Fire extinguishers — ten to twelve years. At the office, we don’t replace our fire extinguishers. We have a company come out to service them every few years.
  • Mattresses — seven years. Do people really replace mattresses this often? We’ve had our mattress for more than a decade, and it has never occurred to me to replace it.
  • Perfume — two years. Good grief. I have one bottle of Polo. It’s almost ten years old and only half used. No wonder Kris hates the smell!
  • Pillows — two years. I’ll admit to keeping pillows longer than I ought. An old pillow is a gross thing.
  • Running (and walking) shoes — 300 to 500 miles.
  • Spices — one year. I like the rule of thumb provided in the article: “To tell if your spices are past their prime, open the bag or jar and take a whiff. If there’s no scent, there won’t be any flavor.”
  • Toothbrushes — three months.

This list is fine as far as it goes, but what about other common household items? Shower curtains? Towels? What about wooden spoons? I always worry that our wooden spoons are harboring hordes of bacteria. I also wonder about multivitamins, and about over-the-counter drugs. I have a big tub of ibuprofen with an expiration date of 2004 — what will happen if I use this?

While researching this subject, I found a list of average life expectancies for major appliances at Mr. Appliance. (I supplemented this list with further research.)

Appliance Average life (years)
Microwave oven
8
Garbage disposal
11
Trash compactor
11
Water heater, gas
9
Water heater, electric
14
Smoke detector
10
Refrigerator, standard
14
Refrigerator, compact
8
Washing machine
12
Dryer
13
Range, electric
16
Range, gas
19
Dishwasher
12
Air Conditioner
10

We have some appliances nearing the end of their lifespans. We bought our first home in 1993. Most of our stuff dates from that time. Our washing machine works fine, for example, but the knob broke off a couple years ago; we have to use a pair of pliers to change the settings and to turn it on. The appliance that worries me most is our 14-year-old fridge: it has begun to make a subtle high-pitched noise, though our food is still properly chilled.

I think that it’s best to use something until it wears out. Once it’s worn out, find another use for it, if possible!

[Smart Money: Here's when to replace common household items, via Alfonso]