We study the direct-sum problem for k-party "Number On the Forehead" (NOF) deterministic communication complexity. We prove several positive results, showing that the complexity of computing a function f in this model, on ℓ instances, may be significantly cheaper than ℓ times the complexity of computing f on a single instance. Quite surprisingly, we show that this is the case for "most" (boolean, k-argument) functions. We then formalize two-types of sufficient conditions on a NOF protocol Q, for a single instance, each of which guarantees some communication complexity savings when appropriately extending Q to work on ℓ instances. One such condition refers to what each party needs to know about inputs of the other parties, and the other condition, additionally, refers to the communication pattern that the single-instance protocol Q uses. In both cases, the tool that we use is "multiplexing": we combine messages sent in parallel executions of protocols for a single instance, into a single message for the multi-instance (direct-sum) case, by xoring them with each other.