“It takes time and resources to build the needed additional ammo dumps of this size.”
Bombs and artillery shells could be placed in woods and covered with tarps.
Russia is a big country.
Russia has millions of square miles of taiga and steppe in its Far East. The Russians could dig holes and bury a couple of hundred pounds of munitions at each remote site, and post a soldier there to stand guard over it (with food, of course; and the Russians could tape his favorite shows; do I have to think of everything?!).
Regards,