How long would it take to reach the far to edge of observable universe if going at 5 miles per second?
You would never get there. Is this a trick question?
"The Edge" of the observable universe is some 45 billion light years away. BUT, it is expanding. Now, light travels at 186,000 miles per second. In your example you will travel 7200 miles per day. You'll have all you can do to make it out of our own solar system let alone out of our galaxy which travels 100,000 light years past us.
If the universe were in a steady state, which as I said it is not, it would take you 45 billion years traveling at the speed of light, which you cannot do.