I bought these in a four pack on a previous Woot! and got a chance to use them on a short Appalachian Trail trek a couple of weeks ago.
These get great reviews everywhere I checked online, and worked perfectly for me on my trek. I expect I will lose the sawyer before I ever reach the 100,000 gallon filtering capacity. There was no expiration date or shelf life indicator on the manufacturer’s packaging. So if stored
The only possible issue I saw was that unless you have a moving flow of water (active stream), the included roll up bottle may be a lot more difficult to use (the opening is the same size as a bottle of soda). In my case, I could fill a 32oz nalgene using the sawyer mini and the included 16.9oz bag in a couple of minutes with no physical exertion (it doesn’t take much force to get the water through the filter, and could even be gravity fed). I plan on placing one inline of my drinking tube of a Geigerrigg hydration bag (also a Woot! purchase) to remove the need to transfer from the small Sawyer bag to another container.
I was extremely happy with its ease of use and effectiveness in filtering the water. I would definitely buy it again when needed. They are much cheaper here on Woot! than in my local REI store.