Remember, the recommended amount of water storage is 1 gal. / person / day. That is under "normal" conditions and is for survival consumption only. This ratio does not include bathing, cleaning, pets or livestock.
Recently I purchased the Sawyer Point Zero Two gravity fed filter system. It's claims to filter bacteria as well as viruses. Viruses are not an issue in today's North American society, but should sewage treatment systems collapse, this could change. The ability to back wash the filter gives it an extremely long life of 1 million liters of water!
The Sawyer still has its limits. It will not filter chemicals, pesticides, or heavy metals. Therefore, we're adding this to our Ceramic filter system. It is our hope that these two filter systems will provide us the cleanest water possible without breaking our budget.