Sometimes I still marvel about how in most time-travel stories nobody thinks of this.

The alternate way of computing this is to not actually discard the future, but to split it off to a separate timeline

Or maybe also another one, somewhat related to the main post - let the universe compute, in it's own meta-time, a fixed point [0] of reality (that is, the whole of time between the start and the destination of time travel gets recomputed into a form that allowed it to be internally consistent) and continue from there. You could imagine the universe computer simulating casually the same period of time again and again until a fixed point is reached, just like the iterative algorithms used to find it for functions.

[0] - http://en.wikipedia.org/wiki/Fixed_point_(mathematics)