That's too long. Russia would run out of juice long before that. You have to remember that the economy is one thing, but there's also fighting spirit, which Russians always had when defending, but rarely when attacking. Many people in Russia think it's not their war and as time goes by and life gets harder there's going to be more and more of them, until finally all who wanted to fight will be dead and the rest will rather migrate than die fighting abroad for nothing.
Or the tanking economy could push more people to sign up to fight because there is nothing else to do and it's the fault of the Ukrainians...
There is no logic to things happening in Russia now. People get arrested for holding flowers. State media is bleating incessantly about bird flu biolabs of the big bad West. A sizeable part of the population genuinely believes that they are defending. 140 million people, there could be enough idiots to feed this war for a long time.
Although the looting "armed forces" don't display much fighting spirit, that's true.
Your problem is that although you understand the Russian language, you are extremely far from understanding the Russian mentality. The Russians need an external enemy, preferably a stronger one. Ukraine? "It's petty, Hobotov." But let's bring here the entire Western world united in a single anti-Russian impulse - this is already something to awaken Russia from its eternal procrastination and laziness, you can already work with this. And the louder the cry of anti-Russian rhetoric, the stronger and more effective Russia becomes. People in Russia do not believe in the lifting of sanctions if the aggression in Ukraine stops, so they say "okay, let there be sanctions, we will live with this." They do not take to the streets to protest like the inhabitants of Europe and do not try to overthrow Putin - on the contrary, his support is growing. Putin gave the people in Russia what was expected of him for a long time - he declared Russia's right to its own sovereignty in order to stop being a raw materials appendage and a gas station of the West. For the sanctions against the oligarchs in Europe, a special thank you from the Russians, they are not very loved here, ordinary people believe that the oligarchs have been robbing the country for decades and exporting the loot to the West. Well, now all the huge natural wealth of Russia belongs to Russia itself. Why would the Russian people berate Putin here? In Russia, Putin is now a folk hero, the "collector of Russian lands".
He can easily continue for another 1-5 years.
Lukashenko said that by the end of this year the world will forget about Ukraine. I'm not sure what exactly he meant, whether there will be a more serious problem in the world that will make Ukraine forget (as the operation in Ukraine almost made the whole world forget about covid-19), or just the problem in Ukraine will be resolved and cease to be such sharp and exciting the whole world, as now.
Let me tell you something else, it seems that in July the anniversary economic forum will be held in St. Petersburg, Russia.
Representatives from 69 countries and territories have already confirmed their participation in the SPIEF-2022 events: Australia, Austria, Azerbaijan, Bangladesh, Belize, Belgium, Benin, Bulgaria, Burkina Faso, Great Britain, Hungary, Venezuela, Ghana, Germany, Hong Kong (China) , Greece, Denmark, Egypt, Israel, India, Jordan, Iran, Italy, Yemen, Kazakhstan, Cameroon, Canada, Qatar, Kenya, Kyrgyzstan, China, Colombia, Kuwait, Liechtenstein, Luxembourg, Mauritania, Malta, Morocco, Mexico, Moldova , Monaco, Mongolia, Namibia, Nigeria, Netherlands, Norway, UAE, Palestine, Republic of Belarus, Republic of Cyprus, Romania, USA, Saudi Arabia, Serbia, Syria, Slovenia, Sierra Leone, Thailand, Turkey, Uzbekistan, Ukraine, Uruguay, Finland, France, Central African Republic, Switzerland, Sweden, Sri Lanka, Japan.
Everyone has the right to draw their own conclusions.