I used T3 during a bulking cycle (@50mcg). And I think it's useless. I was eating a lot (4000 cal) all clean bulking cycle, and I still gained a little fat - no more or less than in similar cycles without T3.
Remember that one of the greatest factors in endogenous T3 production is the amount of calories in your diet... So if you're eating a ton of carbs, your body will already be producing more T3 to compensate.
IMHO don't use the T3, save it for a low-calorie cutting cycle.
I've never actually seen documented evidence that taking T3 can permanently affect your own thyroid in males. Although that is the rumour which flies around everywhere...
The best use I've found for T3 is 'thyroid replacement therapy' as I call it; when you're on a low cal diet your endogenous T3 output is reduced as a homeostatic mechanism, so supplementing with 12.5 - 25mcg of T3 can help keep your metabolic rate high enough to allow fatloss to continue.
If you are running Growth Hormone, or igf-1, with your AAS then T3 use might have a use to maximize your gains on the cycle, but not with AAS only. Don't waste your T3, save it for your cutting cycles!!