OK to upgrade my LTM from 11.6 to 12.0?

12.1.0 was Released last 05/18/2016. You might want to check the release notes: https://support.f5.com/kb/en-us/products/big-ip_ltm/releasenotes/product/relnote-ltm-12-1-0.html And check the Platform support, plus the new and fixed bug in this version, and proactively run on the known issues listed in the release notes too.