I was going to ask the same question this morning actually.
I've made it through to the end of 1940, on my 7th patrol, I just transferred to the 7th out of St Nazaire.
I've gone on a trip through the Channel, taken on a troop-carrying task force in 15m of water up in norway, I got busted on the surface by 3 swordfish and my gunner (who was unqualified i might add) dropped them all, I spent 3 days in game time hounding a convoy in the bight between wales and Ireland in shallow enough water without having a aDC dropped anywhere near me
I did suffer a hell of a lot of damage, it turned out to be 78% damage, by playing chicken with a tribal destroyer because I hadnt seen any contacts in 2 weeks nearby to scapa.. but that was from a deliberate choice - If i had dived he wouldnt have known i was there.
Im lookin fwd to more of a challenge in the later years then, thats for sure
