How many miles across the universe?

The universe is 78 billion light years in radius, 156 billion in diameter. 1 light year is how long it will take you to travel at the speed of light so if it's 78 billion light years in radius then it would take you 78 billion years to travel that far. Also people have said that if you go far enough the number of partial combinations will run out and you will start to see exact replicas of the world you know and love.