Yeah, it’s very vague but I assume since Nolan has some grey hair and there are more elderly looking Viltrumites that there is some limit.

This was my thought as well. With an individual always surviving there was always a microscopic chance that one was the original. Obviously they’re fooling themselves, but how are they going to go through the mental gymnastics now when they know for a fact that neither is the original.

(My guess is they’ll just up their delusions to 11 and nothing will change with how they behave).