They only stop producing if they are destroyed. In order to generate these resources, the Com and builder units create structures that produce them at a constant rate. TA and SupCom had/have two resources - metal and energy (mass and energy in SupCom). In both games, the player begins with a powerful unit called a 'Commander (Com).' The com is a builder, starting the player off with basic resource and unit producing structures, but also acting as a formidable warrior as well. It provides the essentials of what made TA great and adds a number of small, yet useful, improvements. Supreme Commander (SupCom) did not let me down. TA was, in my opinion, the best Real Time Strategy (RTS) game ever made, so even an updated follow up would need to be extraordinary.
From developer Chris Taylor, we have what is essentially the spiritual successor to Total Annihilation (TA).
