It's probably a mix of both. If they win a MNC, they've done everything they've needed to do and they've had a successful year. But playing for a MNC is the goal of every kid who plays at a major division one school, so it's not exactly like we're the only team that talks about it. Every school talks about it if they are in the position to win it.
That said, can you have have an 11-12 win season, make a BCS bowl, win it and call it a successful season? I think so. Can you lose three of your last four, including a bowl loss to a team you beat down earlier in the year, and call it an unsuccessful season? I think so.