Form 8606 Part I is only needed for years that you made new nondeductible traditional IRA contributions or took a distribution from your traditional IRAs. Apparently neither of those things happened (and you didn't mention doing any Roth conversions or nonqualified distributions from a Roth IRA that would require Part II or Part III), so your 2011 Form 8606 is still current and your tax returns for subsequent years should not have included Form 8606.
