What is religion, if not a belief that there is a separate universe of which we can be conscious, and in which we can spend time?
It's a fair question. A religious theory and Multiple Universe Theory differ in this: the other Universes predicated by MUT are places that, even if they exist, cannot ever be interacted with.
Even if MUT were true (and how could we ever know?) we could not ever spend time there, in the same rigorous sense that 1 cannot equal 2.
But a religious theory, if it is in fact a true religious theory, can be realized. One day, we may indeed find ourselves in Paradise.