Take a look around the edges of the spring at both ends. Just like my '07 M8, my 2010 primary spring is making a lot of contact with the spring cup on the cover and spider ends. There are serious wear marks on the spring after 150 miles. Can't say for sure that this is causing breakage, but it isn't good. I can't believe they haven't fixed this problem yet. At the very least, it cranks up the finish rate of your primary spring.
It's pretty easy to remove some material from the cover side. The spider end has a pretty deep cup. You'll have to remove quite a bit of material to stop the contact. Because it's so close to the rotational center of mass, I wouldn't worry too much about balance.
Since the primary hasn't changed from the '09s, and I don't think many '09s had spring breakage problems, it's probably related to the new spring as well. Apparently its the same spring as the orange/white, but from a new vendor. Low bidder I'm sure......