Yes that makes sense. We had one dog off of medication for a year after a crash on vetroyl, so it isn't unheard of. It just depends on how fast his adrenal glands kick in and how much they produce.
I can see the point the vet and Dechra are thinking of with wanting to wait. If it goes up, though, I would go much lower than the 60mg.

Hang in there! You're doing good, heat and all.

Sharlene and molly muffin