Some of this advice may sound like obvious statements, but consider how important having clean(er) watter will be in a crisis...
https://www.backdoorsurvival.com/how-to-make-a-water-filter-last-longer/
I note some important factor about water filters:
1) Cleaning the filter after EACH use is a major factor in how much water it will filter and how fast it will work.
2) Avoid using your filter(s) to make more water than your need for the moment. Yes, you can store some for later use, but avoid wasting any.
3) Not all filters will do the same job. Study each filter to learn what it will do and what it WILL NOT do.
4) If you are only using your filter to remove biological (bacteria, spores) contaminants, consider boiling the water rather than running it through your filter.
5) Use a "pre-filter" and a settling jar to remove large contaminants BEFORE filtering.
6) Cheaper filters may be no worse than more expensive filters. Conversely, an expensive filter may just be a brand name expense that you don't need...