How many years does a franchise last for Madden 12?

In Madden NFL 12, a franchise mode can last indefinitely as long as the player continues to manage the team. Each season consists of 17 weeks of regular games, followed by the playoffs, and players can choose to keep the franchise going for multiple seasons. The game does not impose a strict limit on the number of years a franchise can run, allowing for long-term team management and development.