What is the lifetime of an Rvalue reference?

Question

In C++, you can't assign a reference to an expression that returns a value.

int & ref = 10 + 10; //Error

I noticed, however, that you can assign a Rvalue to an expression that returns a value:

int && Rref = 10 + 10; //This is ok

Does the lifetime of Rref extend until the end of the scope, or is using Rref undefined behavior?

In a slightly more complicated example, let's take a class with a nontrivial constructor and destructor. It manages a pointer to something else.

//These are defined somewhere else
struct State; 
State* makeState() noexcept;
void transformState(State*) noexcept;
void cleanState(State*) noexcept;

//Creates a state and cleans up the state at the end
struct Blitz {
    State* state;
    Blitz() { 
        state = makeState(); 
    }
    ~Blitz() { 
        cleanState(state);
    }
};

void dostuff() {
    auto&& myBlitz = Blitz();
    transformState(myBlitz.state);
}

In the function dostuff, does the standard guarantee that the destructor won't be called until the end of the function?