It can go on for a long time as Russia has a lot of bodies they don’t care about. Ukraine could bring the numbers up, but only through the death of their own people as well: they currently judge this is the best for them. What we really need is Russian Artillery - once that runs out Ukraine has a larger advantage (particular if EU plans to deliver artillery start happening - ideally in vastly larger numbers than current plans)

I’m curious to see is what happens as Russia’s artillery gets scarcer and scarcer. That one is a particularly slow burn, unfortunately.

Really we need the US and Europe to provide long range cruise missiles in quantity. Shutting down (even just drastically slowing) Russia’s manufacturing is the quickest way to finish the war.