I've tested it and the third word of DA and the perk each multiply the duration by 1.5. Here's the breakdown;
1 word does 8 seconds normally, 12 with stability, and 16 with DA & stability.
2 words do 12 seconds normally, 18 with stability, and 24 with DA & stability.
3 words do 16 seconds normally, 24 with stability, and 36 with DA & stability
Remember, DA will only affect duration if slow time is used while under the effects of all three words.
I've tested it and the third word of DA and the perk each multiply the duration by 1.5. Here's the breakdown;
1 word does 8 seconds normally, 12 with stability, and 16 with DA & stability.
2 words do 12 seconds normally, 18 with stability, and 24 with DA & stability.
3 words do 16 seconds normally, 24 with stability, and 36 with DA & stability
Remember, DA will only affect duration if slow time is used while under the effects of all three words.