[Pitch] 128 bit Integer Types

If Int128 existed at the time Duration was defined, would it have been defined differently? e.g. to just use an Int128, or even to just be an Int128?

I'm not sure how important the answer is to this discussion, but maybe it hints at which way the balance is leaning currently.

I assume Duration won't change as a result of this proposal, for ABI compatibility reasons if nothing else?