Yea, usually in my dynasties, about 4 or 5 years into it, my team is stacked and the game has become too easy, so I end up going undefeated for a few seasons in a row. When that happens, I start to lose interest in the game, becuase its not fun to win 63-0 all the time. I usually bump it up to Heisman mode or just start a new dynasty, so my longest winning streak is about 30 games I would say.