On the flip side the longer the war takes the more Ukraine will be useless to Russia. It'd be even worse cuz the rebuilding and continued insurrection activity will be a huge liability. The way I see it, the longer this war goes on Russia becomes less likely to take Kiev and/or win the war. So ya I don't think nuking is even an option for Russia, it's either win conventionally or pull out completely. Ukraine will not accept giving an inch of ground to Russia.