In short, no, unused water filters don't expire. There is no set lifespan for water filters, as long as they are not exposed to moisture. That's the key to making water filters work and, without that, they stay seated and ready to use at any time. The quick answer is yes, all water filters eventually expire.
The material and quality of the filter, the brand and whether or not you have used the filter will determine its useful life. Although water filters don't have an expiration date, they come with a recommended lifespan. If you don't change your charcoal water filter on a regular basis, the water you drink may experience some worrying symptoms. Don't worry, you can still use it.
Replace the filter cartridge with clean water using a carbon filter (activated carbon). Carbon filters can also be used for long-term storage as long as they are in good condition (no dents). Unused carbon filters never run out. Used activated carbon filters can last from 6 months to 1 year.
However, it all depends on the source of the water used and the frequent or non-existent cleaning. Harmful contaminants trapped in the filter will, over time, thrive in the humid environment of the filter media. However, I wouldn't recommend using water filters that have been in storage for a particularly long time, such as a decade. A working water filter should eliminate most of the associated odors by removing them from the drinking water supply.
The best drinking water systems house filter cartridges in a unit from which the cartridges can be easily removed when replacements are needed. Backpacker water filters are advertised to produce between 300 and 500 gallons, on average, although some manufacturers make exaggerated claims that they can last 100,000 gallons. Some filter change indicators work on a traffic light system, so you can buy a new filter when the traffic light turns orange, as it's almost time to change it. Cracked filters should also not be used (usually caused by the freeze-thaw cycle, but accidental damage can also occur), since the substrate barrier is compromised and unfiltered water can flow through, bypassing the filtration system.
The capacity of a filtration system is the amount of water that can flow through the system before the filter media becomes too clogged with contaminants to continue its performance. If your tap water doesn't taste clean anymore, consider how long it's been since you last changed the filter. The filter media will continue to retain these contaminants, and the buildup of impurities on the surface eventually leaves very little room for water to pass through. They have a straw instead of a needle, and the bags are also different, since one filters water and the other doesn't.
If relatively clean water is passed through an activated carbon filter, fewer contaminants will be trapped in the filter media. If you replaced the water filter and you still detect a strong odor in the water, you will need to report the problem to your county health department.