Its not people that Russia will run out of, but instead equipment.
Russia moved from T-72 tanks, to T-55 tanks, and now golf-carts and motorcycles. Russia has moved from 152mm artillery and regular thermobaric rockets to heavy mortar. And now that mortar is getting blown up, the Russians are begging the North Koreans for more shells and artillery.
We’re clearly witnessing the degeneration of the entirety of Russian force technology. Meanwhile, F16s are about to join the Ukrainian side as Ukraine gets more and more upgrades.
Once the equipment runs out, then what? No number of Russians on golf-carts / motorcycles will allow for a match vs a Ukrainian M2 Bradley.