Well, I can tell you this... Blue cats first started showing up in the Potomac River in the late 80's. 20 years later they are reaching the 60 plus pound mark and still growing... They were stocked into the James Rivers river which is a hair bit south of the Potomac River in the early 1970's. The James River now holds the Virginia state record at 102 pounds, 4 ounces!
My guess, a 60 plus pound blue cat may very well be 20 plus years of age in a wild population. In a more commercial setting I suspect younger, but they would have a shorter life span. There are documented cases of blue cats growing in excess of 200 and even 300 plus pounds in the Mississippi River back in the Lewis and Clark days... It is estimated those fish were living in excess of 100 years of age. However, that was under no pollution or degradation of habitat...
Check out this link for lots of good blue cat info including ages and weights...
http://www.dgif.virginia.gov/fishing/conditions/tidal-river-blue-catfish-report.pdf
