Those revenues have to pay not just for the items ordinary Russians need on a daily basis, but also for the massive additional expenditures for the war. I question how long Russians will be willing to do that.
It's also worth noting that Russia never really did defeat Chechnya, which is more than twenty times smaller than Ukraine. They ended up signing a peace treaty that left the Chechens with a lot of autonomy.
The Russian tolerance for dead Russian soldiers is not unlimited.
Yes: Putin does not have the Soviet Union’s ability to command 40% or 50% of Russia’s economy to support military operations.
Russia can afford a lengthy engagement. The Chineese have encouraged them in that direction. A lengthy engagement will keep oil and mineral prices high. Fertilizere and wheat will not be sold. This inflation will hasten the end of the dollar as a reserve currency. This is the Chineese strategic objective.