Most fitness gear can last for years but some gear may be used way beyond their expiration date. It doesn't hurt to update or even upgrade some of your equipment.
Running shoes - Often you can just take a look at the soles of your favorite running shoes and know it is time to toss them. However, for most runners, the average length of time your shoes may last is between 350 - 500 miles. For those who run at least 25 miles per week, the recommendation is to get a new pair every 3 to 4 months.
Bicycle helmet - Bicycle helmets should be replaced after any crash. The foam inside may not be as protective after an impact. The same goes if you have dropped your helmet on a hard surface and have cracked the foam. If your helmet is very old, it is a good idea to get a new one that meets current safety standards.
Bicycle - A bike frame can last a long time, at least 20 years if stored properly. The gears and chains can be changed every 5 to 10 years depending on wear and tear. A visit to your local bike shop for a tune-up will let you know for sure what kind of shape your bicycle is in.
Yoga mats - These may last for quite awhile but if you're noticing some wear and tear, it's time to replace it. You can even recycle your mat.
Gloves - You may use gloves for lifting weights. Most have padding where you grip. Check to see if the padding is getting worn down.
Fortunately, there isn't very much gear required to stay fit unless you participate in a specific sport or other physical activity that needs special equipment. What have you replaced lately?