Oh, okay. So how long is that?
Remember that there is a running clock here.

I agree - and the running clock favors Ukraine, rather than Russia. The militaries and economies of the combined NATO powers absolutely dwarf those of Russia. At some point, if Russia can't defeat the Ukrainians (which they have failed to do for three and a half years now), it will be difficult for even Putin to maintain the illusion that they might actually be able to conquer the country.

And what should be obvious to you that in Realpolitik possession is 9/10 of the law.

Ummmm, no. History is replete with examples of large powers that invaded smaller ones and "possessed" large portions of them....and then couldn't hold them. Ukraine can't displace Russia, but Russia isn't going to be able to hold onto what it "possesses" if Ukraine keeps fighting them.

Do you think the Russians didn't learn anything from their own Afghanistan adventure, or ours? Or us in Iraq?
What might they do differently this time?

Not very much, no. Like all those other times, Russia appears to have assumed that since it had the overwhelming conventional forces of a much larger army (and a much larger country than Ukraine backing them up) that it would be a relatively simple matter to win just by invading. They don't appear to have learned any of the lessons of asymmetric warfare.

In fact, they seem to have completely repeated the mistakes we made in Iraq. By all accounts, Putin appears to have completely bought into the idea that Ukraine wasn't really a country and that they hated the Zelensky government and were really Russians anyway who would be glad to be invaded. His own version of "greeted as liberators" and "candy and flowers." There's zero chance that he actually contemplated that he would encounter bitter resistance and that his invasionary force would be fought to a standstill for more than three years.