That's what I'm saying. The runtime will go down to a constant. It can't keep decreasing forever.
This is possible because we are sampling a probability distribution. A dice is discrete but the probability of rolling a 1 as the number of sides increases tends to zero even if there is a whole “1” in a given dice.
it's not possible for it to behave differently as n increases because it doesn't have enough time to distinguish between different values of n once it's large enough.