umm, did my math wrong as well
because for the first empowerment point you get a much bigger bonus then for the other 4 you put into a single skill
the fist point increased the buff's duration by 3.5 seconds, the 2nd one only gave another 1.0 second. with my 2 points into it the skill lasts for 8+3.5+1 seconds.
so the max seems to be 15.5 seconds with 5 points added into it. still, its more likely that the 1040 points of absorbsion will get used up faster than that time is up