https://en.wikipedia.org/wiki/K2-18b

Resolves once conclusive evidence comes out either way. Perhaps we'll find out that it's not dimethyl sulfide at all, or that there's some abiotic way of creating it that's happening on K2-18b, or we'll find other unrelated signs of life to confirm that it's there.

Unlike all the other markets about K2-18b, this one stays upon for as long as is necessary to find out for sure. So it could be a while, but this is the "real" number, not just "will we find out within a certain number of months".

(This market is about whether the recent discovery is valid, not about whether there's life at all.)