Back in the day (last gen) when both games where really good I use to alternate seasons between NCAA and Madden. Basically, I'd complete a season of NCAA then a season of Madden rinse and repeat. This gen I've always given in to the Madden Monster and given up on NCAA once Madden dropped.
This year so far has been the exception. NCAA is such a great game, near perfect, IMO. I bought Madden on day one, played it once and then put NCAA back in. Now, I'm not saying that Madden is a bad game or anything. I just don't feel like looking for and tweaking sliders when the sliders that I use for NCAA work wonderfully for me.
My current plan is to finish one more season of NCAA (that would make 3 complete seasons). A season for me usually take about 2-3 weeks to complete. Once I finish my current season we will be closer to the actual NFL seasons therefore roster's should be a little more accurate. So that seems like the perfect time to start Madden then. My plan is to then catch up by playing 3 season's of M11. Once I complete those season I will start alternating seasons just like I did in the "good old days".