It depends who has the will to last the longest. In reality, if the west had the will to continue supporting an ally, we could bring Russia to it's knees. It's economy is on life support through a war time economy, this will keep it going for a couple of years but is not sustainable long term. It just isn't.
The west's commitment to this war is virtually nothing. The USA would spend more destroying old stock. They don't send them their latest equipment, it's a win win without sending a single soldier to go and do the dirty work. The problem the West has is a lack of resolve, I guess that's natural of living in a democracy. Governments can change and alternative voices exist with a platform, as opposed to filthy dictatorships that murder and imprison everybody against them.
We have paid agents such as Tucker Carlson free to spread filthy dictators lies and misinformation for millions to view, if he was on the other side doing the opposite he'd be in deep Siberia by now.
As long as Ukraine have the desire to fight for their existence, we should back them to the hilt, otherwise History will not judge us favourably.