hmmmm...I think "get tired" is a poor choice of words on my part.
I would never return from a patrol unless I had expended all of my torpedos or recieved to much damage to continue safely.

For instance. I was given a patrol area in ET. I had burned almost half of my fuel in high seas & I was not even half way there yet. As luck would have it, I ran into a convoy and shot up all my torps, so I was able to return with my honor intact even though I didn't go half way around the world...lol...

This way I can still go all the way to ET on my next patrol by refueling & doing the null thing & still get my renown. It is just A-Way...