Putin wants to conquer Ukraine. Ukraine can't surrender.
Therefore they can fight for another 10 years. Easily.
Ukraine cannot fight for ten years. Their armaments come from the West and the West will eventually tire.
I don’t think Russia cares about western Ukraine; they just need to keep their Black Sea Fleet in Crimea. Crimea is the prize they are fighting over and Europe can’t stand that Russia controls Europes needed resources by itself. Without Crimea, Russia would unravel so they will burn the world down before they surrender Crimea.