Seems a deadline like that tactano may perhaps at some level be as much about 'disproving' the inability of T3 to help in your situation, or being seen to have complied as it is about getting you well.
Situations like that are not ideal, but not uncommon it seems. Quite a lot depends on what exacly he meant by allowing eight weeks.
It's sometimes necessary to be careful how you phrase your feedback in that sort of situation - or even to think of possibly moving to another doctor if the situation seems clearly to suggest that stones may be left unturned.
An eight week trial might alternatively prove the basis of a big step forward - and given the problems some of us have have experienced in accessing a trial of T3 (many years of effort and €100s in fees) it's not an opportunity to be sniffed at.
The required dose can be highly variable by all acounts. At the other end of the scale to ND 20mcg daily with T4 wasn't quite the final answer in my own case, but taken with T4 was enough to end my severe hypo symptoms and restore a very reasonable quality of life.
There was an immediate and obvious positive effect in my case, but equally the full benefit took months to filter through - it seems reasonable when we've been hypo for a long time that the body may take a while to find a balance again.
One concern about an 8 weeks one dimensional deadline in principle (in addition to the issue of optimising the dose) is that is it'd be a pity if it was to deliver a false negative. i.e. if it turned out that something else is needed to let the T3 do its job. (purely an example - but maybe adrenal work)
Wish I knew ND how you can manage to take 160mcg of T3 daily. How the body handles it without problems that is - it'd be an enormous dose if it was all being used. It'd blow my head off - i'm up to 40mcg T3 lots through the second half of the day and down to 50mcg of T4 - but add another 5mcg of T3 to that and my pulse starts to climb uncomfortably and so on.
The pity in all of this sort of thing is that it's pretty clear that in an ideal ideal world a doc would follow a (not necessarily one size fits all but symptom and other data led) protocol to prepare a patient for and carry out any trial of T3 - one which would maximise the chances of success while minimising the chances of a false negative....