Russia will likely have more time than we expect. North Korea are proving to be more helpful than expected and have tons of old Soviet era hardware that they would be willing to sell in exchange for some more rocket tech or nuke stuff.
China would also likely be selling their old Soviet era hardware they might still have kicking around. A lot of countries around the world see Putin as desperate and rich so they will be happy to make some money selling older hardware back to the country that made it. Putin likely sees this as fine since the hardware works with the existing forces.
But the money and favors aren't infinite. Putin is still dying of old age and disease. It's a long road but Ukraine is destined to succeed.