Every two weeks you should be boiling your sponges in hot water to kill bacteria. You should replace it as often as possible.
Similar to bug spray, sunscreen doesn't last forever. You should be replacing your bottle every year. If you don't, you won't be getting the protection you need against the sun's harmful rays.
Brushes should be cleaned out at least once a week. A bowl of soapy water and a toothbrush are an ideal combo to help get any bacteria out. Your brush should be fully replaced at least once a year.
Though you wash your towels fairly frequently, they still need to be replaced about every two years. They can still have bacteria on them that cannot be washed out.
Yes, they're probably comfortable, but your old slippers should have been tossed a long time ago. It's recommended that you replace them every six months, especially if they're not washable. Mold and fungus can grow, which can lead to health problems.
Every two to three years you should be replacing your pillows. Not only can they lose their shape, causing spine problems, they can also collect dust mites and other bacteria which could be harmful to your health.