Lots of good information at this site in addition to the products they sell:
Good InfoI use two filters, the first is a 1 micron particulate filter and the second is a 1 micron charcoal. Depending on the site I'm on and the water source my particulate filter lasts anywhere from 2 weeks to 6 months. The 2 weeks is from a county water system in Florida. The water tastes fine, it just has a lot of particulate matter in it.
Someone on a forum recently told me if I switched to a 5 micron filter it would last longer. I resisted responding that if I didn't have a filter at all it would never need placing. Oh well. Filters for my system are not expensive and 1 micron makes me feel better.