Ukraine has been bombing Moscow and Putin's residences and assassinating his friends without any nuclear retaliation so we can be reasonably (if not completely) sure that if the mafia boss were trigger happy we'd know it already.

The truth is that no one has any idea how the war will unfold and attrition can simmer a long time without any clear resolution or winner at all, even between seemingly unbalanced belligerents. See Iran vs Iraq, Saudi vs Yemen, USSR vs Afghanistan, etc. People who are too used to video game map painting tend to underestimate the capabilities of million-strong modern states engaged in an existential war - as the saying goes, there is a great deal of ruin in a nation.

The only conceivable way this resolves in the near future is if Putin gets offed somehow but given how mortally scared he seems to be of drones and his own elites it doesn't seem likely