@C133,
C133 wrote: . . . I assumed that the problem with "semper tua" is that it doesn't
really specify what exactly is "always yours", whereas "semper tua sum"
explicitly states "I am yours always/forever". . .
I believe that
semper tua translates "yours always" very well. Just as
"always yours" does not explicitly state "I am always yours", so
semper
tua does not explicitly state
semper tua sum. If you would use "always
yours" in English, then use
semper tua in Latin.