I'm going to speculate that it's going to take a long time still.
Putin's political career and his legacy are tied to this conflict. In the process he also tied the fate of Russia itself to the conflict. He is willing to sacrifice everything to get a "win", of any kind, which maybe just getting Lugansk and Donetsk, and hopefully, Zoporizhia because it connects to Crimea.
And even if Putin croaks before the war is over, or retires, the reality is it's not going to end. There needs to be a realistic exit strategy for Russia but there isn't at this point. The next leadership would have to contend with exiting a war that may cause a dissolution of the Federation itself. There are a lot of Republics and Ethnic groups that are eager to have Ukraine win – because a weaker Russia means they can withdraw from it.
On the other side Ukraine is going to fight as long as it can, as long as it takes, and the rest of the world is going to support it, because Ukraine losing the war would be disastrous for the European continent and the US's world order. In fact, it would be the biggest break of a taboo over conflicts to conquer territory. If Russia wins it's going to deeply undermine the UN's prohibition of conquest for land, and in doing so a lot of countries with horrific borders (thanks post-colonialism) is going to break out into war. Russia, will, of course support them, so will China.
The US is unwilling to go in 100%, and the Biden administration is too cowardly and too myopic to see what's happening on the horizon. Europe is not yet military ready to deal with Russia. Not yet. But it's increasingly likely that eventually a NATO war with Russia will become inevitable.
And frankly, I don't particularly see anyone in the media or the political circles talking about "the day after" in Russia v Ukraine. I seen it from day one when Gaza and Israel went to war, and the Biden administration is demanding there be a plan for the "day after" there. But no one is talking a bout the day after in Ukraine v Russia. Especially if Russia loses.
What happens if Russia does begin to destabilize and dissolve? What are we going to do about all the nuclear warheads – suddenly you may find an additional 5-6 nuclear armed countries on the world stage.
What happens to the Russian rebels in Donetsk, Luhansk, and Crimea? It would be absurd for Ukraine to want to keep them as they will inevitably create an insurgency. I am 95% certain you will see an ethnic cleansing either forced or not, because a lot of them will be viewed as collaborators of some of the worst atrocities, at best, or outright traitors at worst.
What would we do prevent revanchism that will give the next prince of Russia a carte blanche plate to start over? To conquer the weaker smaller former Republics?
What happens if Russia wins and we see a Russia that holds control over 20-25% of the entire globe's food supply, and is more than happy to use it for it's own geopolitical gain? What if Russia's success leads them to now want concessions and territory from Moldova?
Nobody is asking these questions. No one. I think it's because everyone, left-right, American, European, wants everything to go back to status quo, in every conflict. I think that's honestly the policy of the Biden administration, to reverse time to October 2016. But it's not 2016. I just don't see a vision for America's let alone the West's role in the future of the world. China has a vision for its role. Russia has a vision for its role. But we, in the West, certainly do not. Europe just seems to want to survive it's own domestic and economic crises, and the US is increasingly looking bewildered.