They have air superiority since the start of the conflict and can strike Ukrainian positions with near impunity. With Ukrainian populations depleted, there is no round 2, only where Russia decides to stop pushing.
All far ahead hypothetics.
What exactly does Russia need to rebuild? They've lost less people than US did in Vietnam, and far less materiel (where for example US lost 5000+ helicopters alone to allied forces). US didn't exactly need to rebuild post Vietnam.
He's not lol. They've gone on record saying that they're not gonna negotiate with Ukraine anymore.
Push continues until either NATO sends so many troops/support they can stall it, or until Russia is done.
Putin has shown a consistent track record in the past to negotiate early ceasefire agreements and not going all the way, minimising costs.
He is a risk taker but also very cautious. He is not a war mongering maniac. If its more beneficial to keep taking more of Ukraine in smaller chunks at a time, taking breaks in between, he might take it.
While taking a break for a few years, It might make more sense for Russia to rebuild its army and air force to be able to fight in the modern battlefield with overwhelming force. Building up its stealth fighter fleet for example, or building a huge stockpile of missiles to do a truly massive barrage at the start of round 2. It could also build its ground force to the size of several million like it had during the soviet times. All of these improvements could raise the chance of a sudden blitzkrieg like victory in round 2.
Instead of grinding away slowly for several years, what if they pause for now, then rebuild their air and ground force in such a way as to neutralize Ukraine's air defenses and Ground Force and then do massive blitzkrieg couple of years from now and knock out Ukraine for good in a few days. That could be much less costly than keep fighting now.
But again as you said, there are risks to that approach as well. Maybe its better to keep fighting now and finish the job. We don't have all the facts. Probably not even Putin does. Decisions are often made based on imperfect information and priorities at that exact moment. Situation could compel Russia to pause early and rebuild. Or maybe this war could go on for years. Let's see how it plays out.
