Russia can sustain this war for 4 years more politically (they probably have to finish by 2029, a year before elections), maybe 2-3 years more militarily and economically. I won’t be so sure that Ukraine can last that long, because Ukraine does have people problem and Russia does not. Ukraine even with Western supplies gets a fraction of what Russia currently produces in ammo, missiles, tanks etc. So there is no reason for Russia to accept shitty terms. They may pay 200-300B from the frozen money in „reconstruction support“, but that’s it.