Its appearance has not changed Tom, our perception of it has. Just because we were not viewing it hundreds of years ago does not mean it did not appear curved.
Why stop at hundred of years then? Why not thousands, tens of thousands, or millions?
If we did not view any curving to the horizon prior to the 1940's then there is no reason to say that the "earth has appeared curved for hundreds of years." It's not "appearing curved" if no one is looking at it.
Its a slippery slope slop you are traversing. You are correct, the only thing to assume is the earth is infinite as well as the time from its creation. Unless of course there is evidence otherwise. That is what zeteticism should teach us. Trust our senses, not insane induction that things must have been something.
I'm not going to have some sort of "tree falls in the woods" in the discussion because I think we both understand that there are views that differ there.