Five year rule

As posted in these forums:

Five Year Rule) If you have had the same rating for five or more years, the VA cannot reduce your rating unless your condition has improved on a sustained basis. All the medical evidence, not just the reexamination report, must support the conclusion that your improvement is more than temporary.

I was granted 70% SC for mental condition on Feb 18, 2011.  Date of application was January, 2010.  In either case it has now been over 10 years regardless of which date is used so SC status is secure, though rating percentage is not.  I was granted SS disability in 2018 for the same reason as the VA SC rating, on the first try with no appeal.  Does SS determination create an automatic presumption against lowering of rating, or greatly argue for not “improved on a sustained basis?”  I have put off applying for TDIU for a while but believe I should now.  I have an application with the county rep prepared and ready to go.  I am 65, have not worked since May 2016.