With the current setup in epics 15 seconds is just too long.
TWFers lost their double-procs and the saves all went up by 4 in U9. My fighter's 50 DC stunning-blow lands so rarely that it's not worth the feat/APs.
The fort saves need to stay as is otherwise the insta-kills would be even more of a joke than they are now but a shorter cool-down will make SB more viable.