So long? I thought Ukraine was winning so much? If they've killed 100,000 Russian soldiers and destroyed 500,000 Russian tanks surely there isn't much left? How are Russia going to drag it out for years?The war will last for years, Ukraine has plenty of time.
It's Russia that has time, not Ukraine. Look at the state of both countries. Ukraine is fully mobilised with mass conscription, while Russia has only dedicated a small portion of it's army to the fight. Ukraine needs to worry about every barrel of oil, every truck load of supplies that is coming over its borders while Russia is trading with the vast majority of the world normally. Economy/military Russia is doing fine on their own (in fact record revenues), while the whole Ukrainian state is dependent on handouts.
A long war is possible but unlikely. I think it'll be done by the end of the year at most, but we'll see.