Does the filter ever get old? I have one of the "PUR" hikers before Katadyn took over. The filter was fairly new the last time I used it but it has not been used in about 5 or 6 years. Any need to replace the filter or the entire unit?

Jeff (as always) is correct, but let me add more. Inside the filter is activated charcoal. It is very stable until you first run water through it. It is then "used up" in about 6 months. No problem when the charcoal is "used up", except the charcoal improves the taste of water and removes organic chemicals. If you are filtering downstream from agriculture or industry: the charcoal removes herbicides, pesticides, and other stuff that is not good for you in the long run. So----if you are worried about taste or chemicals, buy a new filter. Otherwise, be like my fishing buddy: who has used the same filter-cartridge for the last 12 years. One note: remove the clip that holds the pump in and lube the black O-ring on the pump every year or so with the supplied silicon lube. A dry O-ring can make you think the filter is clogged.

Your filter is already old but that doesn't have any effect on it's performance. As long as it pumps easily it's working fine. Pump some clean water through it before your next outing & evaluate the results.