Wow, another person familiar with the adventures of dear old Richard Camellion. I have a perverse fondness for those books because they're so insanely over the top, not to mention all the sci fi/paranormal bizarreness Joseph Rosenberger went for.
It's interesting that like the Punisher the Executioner is still an active character, along with the characters originally created for the spinoff Able Team and Phoenix Force books. All the rest of the titles that came out of the '70s pulp era are gone. Even the Destroyer, which survived into the 21st Century, may have seen its last book release after Warren Murphy had a falling out with Tor Books, which had become the new rights holder after the previous contract with publisher Gold Eagle ended.(There's a Destroyer film in the works apparently.)
Like many comic characters Mack Bolan increasingly faces continuity problems, since his back story still has him as a Vietnam vet even though the stories are set in contemporary times. So you have a man who at the youngest is in his early 60s running around fighting like a man in his prime. Some of the supporting characters must be even older.