What is the optimum time to replace a standard Brita water filter?

ackmondual asked: I used to replace my filter every 2 months as suggested on the box. Currently, I’m using the same filter since middle of March ‘07, so I’m running about 5 months now. Now that I’ve noticed it, the box actually says “2 months OR 40 gallons” for best results. 2 months is definately long due, but i’ve been keeping a tally, and I’ve consumed about 85% of the 40 gallons (I get ALOT of water where I work since there’s a water cooler/filter there, and unlike the box which assumes a family of 4 as typical use,... 

What is the major difference between a water filter, purifier, softener or conditioner?

kimemeki asked: I have a private well system here in Wasilla, AK and I am not happy with the water quality. I used a shower filter to remove chlorine etc when I lived in California but that is not the problem now. The water causes dry skin, tastes horrible and seems to have a lot of calcium and iron in it. I had some tests done and was offered a Water conditioner that uses polymer beads and a seperate system that uses reverse osmosis to filter and soften all of the water in the house. This will cost around $3000 is that the best way to go or does anyone know of a better option?...