how often do i have to buy a new filter? you're all talking about using it camping. i want it as back up at home during hurricane season when we lose city water and have to rely on tea-brown, sulphurous well water. i'm after something that isn't going to lock me into buying wasteful plastic filters (like the ones on my brita water filter jug).

Replacing the filter cartridge depends mainly on the quality of water you're filtering. Clean mountain stream water as compared to "tea-brown, sulphurous well water" would have better results for longer cartridge life. I can filter approximately 150 gallons of "cmsw" before back flushing. With "t-bsww" possibly 50 gallons & replacement after 100. These are very subjective numbers which warrant actual usage for proper determination. I can safely say you would have better results with the First Need as compared to the Brita water filter jug. I've used mine in third world countries with good results, in other words, I've never gotten sick from drinking tainted water.