The Russia won't run out of military equipment anytime soon. The most important reason to destroy it is that it's expensive to replace. And when it comes to air defence radars, also not really all that possible to replace.
What brings the war to end is economy. The Russia's economy won't survive very long anymore, and once the state is bankrupt, it no longer can pay the high salaries to its soldiers. Since the soldiers are in it almost exclusively for the money, that will mean there will no longer be new soldiers to replace the losses.
The Russia can of course print more money, but that will cause inflation, meaning that the soldiers' salaries need to be raised more, which increases the need to print more money, which... :)