Russia building large scale military infrastructure on European border
pravda.com.ua
pravda.com.ua
That's mostly a theoretic scenario imho:
Suppose there's a cease-fire, and Russia moves a mass of its troops near the Baltic states (to "poke" those, or worse).
What would stop Ukraine @ that point from grabbing the opportunity & regain Russia-occupied territory?
In short: those Russian troops aren't moving until there's a durable end to the war. Which Putin doesn't seem to want.
I suspect it's a matter of time before Russia's economy and/or its leadership cracks. At which point things will happen fast. And replacement Russian leadership probably won't have appetite to continue the war (or go dance with NATO).
Lack of man power.
That's a myth that economy can improve by military spendings. It boosts production and investments in the moment, but in the long run it sucks resources out of economy. USSR failed precisely because of dozens of years long high military spendings