There is absolutely NO NEED to taper once you decide you want to go off. In fact, it is a BAD idea. Gradually reducing your T3 dosage does NOT result in a quicker recovery...it prolongs it by exposing the body to the suppressive effect of the drug for a longer period of time. Just like with AAS, the body will not begin to recover its own production of T3 until exogenous T3 is eliminated...or nearly so.
We also used to believe that tapering steroids was the right thing to do. Bro-science claimed that by gradually reducing the dose, the body would not be exposed to a rapid decline in hormone levels and therefore, would escape the "shock" of a hormonal dive-bomb. In terms of recovery, we also thought that if we gradually reduced the dose, it would "prepare" the body for producing its own testosterone by more subtly bringing our hormone levels back to normal.
However, what we didn't understand at that time is that steroids, even at low dosages, still retain their strong suppressive influence on the HPTA. By gradually reducing the dosage, all we were accomplishing was making recovery take even longer! It is the same with T3. If we want to recover from exogenous T3 as quickly as possible, we must eliminate T3 completely, all at once. This way, the thyroid gland is forced to resume production at full force, as it attempts to correct the deficiency. If we graudally reducing the dose, the body doesn't have any sense of urgency when it comes to restoring maximal production, as it is still being supplied with exogenous T3.
In conclusion, when you are ready to end your cycle, do NOT taper. Tapering with T3 is a myth...100% bro-science with no scientific validation. You should treat T3 just like you treat AAS...get in, hit it hard and when you're done...you're done. None of this fucking around, gradually reducing your dose bullshit.
It is also a myth that using T3 beyond 9 weeks will permanently shutdown one's natural production. Studies have shown that even a full replacment dose of T3 taken for nearly a year did not result in permamant suppression, with users experiencing a full recovery within a relatively short period of time after discontinuing exogneous T3. In the real-world, numerous individuals have run T3 for extended period of time and experienced a full recovery after just a few months. Still, in my opinion, T3 is not a drug which should be used long-term just for the hell of it.
As far as tapering from the start of the cycle, this is generaly a good idea if you plan of going above 50 mcg per day. At doses of 50 mcg and under, a taper is not needed. If you don't know what dose is ideal for you, it is wise to start on the lower end and gradually work up as needed. If you start off higher than what you need, it could negatively affect lean mass retention.