There have been a few studies looking at the effect of age on rotator cuff tear surgery. These same studies also look at the size of the tear as a possible factor in the results.
Not too many people in your age group have this surgery. Results are mixed without a clear conclusion. Shoulder motion and function seems to be better in the younger age groups even before the operation.
Smaller tears seem to have a better final result in all age groups. Some studies have mixed results. In general researchers are unable to reach a final conclusion about the effect of patient age on the outcome.