I) It's safe to be on long term so long as its real T, not the supplement stuff. But you must tell a vet as it can interact with other medications and you would absolutely have to tell them if you were going in for emergency surgery. You'd also have to stop prior to routine surgery just to be safe.
II) Scottie and I used it for ... 6 ish months. I stopped because I read there was a possibility it wasn't compatible with his anxiety meds and when I no longer had the drive to make it for him I stopped making it for myself. I noticed a huge difference when I was on it - so can only assume he felt better on it too. As I mentioned in on the other thread - I have a bad back and knees - didn't think it was helping much but then missed a few weeks worth of doses and really noticed a difference in my self.
III) Start small and work up to a larger dose - I think its about a tablespoon over the course of the day. You don't want to start high - it makes you poo like no ones business. I accidentally O/D Scott in the start and he did like 4 massive poos while we were walking around the block - poor boy. I think, from memory, it has a short half life (is that the right term here?) so it doesn't stay in your body long - so smaller doses more often is more beneficial.
There's a very active facebook group - the Turmeric Users Group - if you're interested.
In short, I highly rate it and say so long as it doesn't interfere with other meds give it a try. As a side note, it is messy (I preferred making it with coconut oil to give it some structure), tastes nasty as hell and you can overdose on it - an acquaintance of mine reported getting dizzy and faint headed after discovering Turmeric chai lattes and adding a lot of them to her diet on top of golden paste.