I have 11 years to go until 60. I reckon I'm better off going to 60 in FTRS than I would be in the Regulars as my accruel rate is faster than on AFPS75.
I would just be careful that you don't leave yourself more vulnerable in case of sickness/illness on FTRS. Your 50's can reveal many physical problems and, I think you may be better placed as a regular if something occurred. How would you stand if say, you became unfit for service at age 55 as FTRS?
OAP