The Stone would make his transfiguration permanent and thus presumably render them immune to Finite Incantatem. If he doesn’t use the Stone (e.g. in the case of Voldemort, which you are probably referring to), I don’t know of any conventional way to proof against F.I. (Knowing Harry, I’m sure he’d be able to think of some rather unconventional ideas if he sets his mind on it.)
I hope Voldemort’s “fallback weapon” also had sunlight-resistant skin. Otherwise Hermione might have issues with going outside...
I also take it that Harry’s refusal to give Quirrell’s eulogy even before he knew Q = V is because of his views on death in general.
Speaking of the eulogy, is Harry cheering at the end? And does he have any way of protecting his Transfigurations against Finite Incantatem?
The Stone would make his transfiguration permanent and thus presumably render them immune to Finite Incantatem. If he doesn’t use the Stone (e.g. in the case of Voldemort, which you are probably referring to), I don’t know of any conventional way to proof against F.I. (Knowing Harry, I’m sure he’d be able to think of some rather unconventional ideas if he sets his mind on it.)