How to protect against ephemeral key reuse in some signature schemes?
Would you say: the probability of mass life extinction on earth caused by asteroid impact is like $2^{-28}$/year; but the risk is so big that I think it's worth taking some countermeasure?

The applied cryptographer's position is that below a certain probability, like $2^{-40}$ lower than mass life extinction on earth, there's no need to mitigate the risk. It is best to spend effort on countermeasures against a stuck TRNG, by accident or attack.