Depends, Both the Ukrainians and the Russians are spending several times their current production of shells and other munitions. Ukraine is getting resupply from NATO and other countries, who will be several years rebuilding their stockpiles. Russia is consuming their stockpiles that may date all the way back to the end of the second world war.
Shell shortages are not a new phenomenon in war, in 1915 all participants in WWI had fewer shells than they wanted. Once the pre-war stockpiles are consumed both sides will be limited to production rates for shells, and the production rates will be a moving target.
The Russians have far greater manufacturing capacity than we do or NATO countries do as a whole.
This ridiculous claim Russia is running out of ammo and weapons has been made since last March and its been consistently wrong.