Wikipedia lists a total of 14000 tanks, reserves included, (majority being T-72 and modernized variants) + unknown number of T-54 and T-64. I suppose even the russians don’t know how many of those are in combat ready shape by any stretch, but apparently at least a half (not counting ones they’ve bought from elsewhere).
So, as the war has been going for two years that 1-2 years more sounds plausible. If current news are anything to go by I’m quite afraid that Ukraine doesn’t have that much unless they really start receiving reinforcements from Europe and US. And should Ukraine collapse it would take 5-10(ish) years for Russia to rebuild enough hardware to do the very same thing with some other country. Maybe not with a NATO country and maybe not one the global west is as interested as Ukraine, but it could (or would, depending on which prediction you want to follow) happen.
Plus the wild card of China, who no doubt are following the situation and spesifically western response pretty closely. I wonder what happened to those 800 000 artillery shells Czechs promised to gather…