then it will take years...
I don't think that many more. The economic issues are finally taking a toll. And at something like 1000 dead soldiers a day plus the huge losses in drone strikes on expensive military targets and oil refineries... there is gas rationing in Crimea now... this will soon drive what were lower middle class Russians ( that aspired in resource rich Russia to enter the middle class in Europe ) into the poor house and their anger will eventually cause the Putin nationalist empire / oligarchy to fall. What replaces it will be interesting. But they will withdraw from Ukraine.
Russia has learned some hard lessons on asymmetric warfare and are now starting to deploy their own drone attacks on Ukraine infrastructure. But Ukraine is made of some very tough people. I don't think Russia can defeat them... and even if Ukraine surrenders, Russia will constantly be fighting a nationalist resistance campaign in Ukraine for decades if not centuries.