Strategy to deal with multi billion row simulation results and partitioning
We were doing something not unlike this with clickstream data.  We unplugged SQLServer and plugged in Vertica (a columnar analytics ANSI-SQL compliant RDBMS)...we've never looked back.  Multi-minute queries dropped to millsecond queries, and data loads dropped from hours to seconds. If/when you start outgrowing it, add more nodes and rebalance online. Very nicely done product.

The Community Edition is free for 3 nodes and 1Tb of data (which gets compressed a LOT more than you would expect, so 1Tb is quite a lot of data), and the commercial version (unlimited nodes) is about half the cost of SQLServer EE for TB-size data (it's licensed by data size).  You might want to give it a look. ;-)

Btw, I have no affiliation with Vertica or HP, I'm just a very pleased customer/data architect.

Cheers,
Dave Sisk