Just to further clarify, to my knowledge a patent has a 20 year life span. There may be some continuity data that goes back to 1995 on patent 6598148. Regardless of 1995 or 1998 as you suggested, it would appear based on this that the patent's natural life might have expired in 2015 or 2018 if the maintenance fees had been kept up to date.

Regardless, PTSC's website says 2015. If one of our most valuable patents expired because its time ran out, why is Patriot telling the world it's 2015.