Ju 88's seem fairly durable in a scenario setting. I don't think that the wings are fragile -- just that they are full of fuel and a bigger target if the enemy is above or below. Often, I would lose other parts (elevator, rudder, vertical stabilizer, flap, engine oil, fuel leaks, coolant, engine fire, fuel fire) before a wing would come off. Also, it seemed like the wing would come off only after a lot of enemy fire into it. In cases where a plane approached level, enemies would sometimes concentrate on the fuselage. This happened for example in a P-39 attack, and my elevators, rudder, and finally vertical stabilizer broke, but not the wing.