I had 2 instances of SSMS open, one was 2008R2 the other 2012.
Each had 4 different tabs open.
I closed both of the SSMS down, and then restarted, 2008R2 first then 2012.
All 8 tabs reopened in the first (2008R2) SSMS.
No tabs were restored in the 2012 SSMS.
OK, this is a weird scenario, but wondered if SQL Prompt could remember tabs based on SSMS.
Annoyingly though, if I had 2 SSMS 2008R2 open each with 4 tabs, then I would expect all 8 to appear in the first invocation of SSMS.