So /vp/, breeding for perfect/near perfect IVs. With the introduction of 5 IV passing from destiny knot it's become a lot easier, but what's the best point to start using it? For example I've got a pair of parents with 3 sets of perfect IVs each, but both have them in the same stats, is it better to use the knot and wait for that one randomized stat to bring up a 31 in one of the others, or to use a power item to get one guaranteed stat and wait until some of the other stats to come up 31 before switching to the knot?
I ask since I've been doing the former, but despite getting a full box of hatchlings with 3 perfects, I've thrown away a fair number with just 2 and have yet to see any with 4. So what do?

Also any other questions about breeding in general not covered in the masses of FAQs available can be asked here I guess. Pic only related since it's what I'm breeding currently.