There are long term gains from running after quitting for years even when you are getting long in the tooth.
Here is a lot of nonsense to back up my half baked claim
Age Time Distance Weight Training
43 6:11 1600 140 no training (estimated from age graded 5:40 mile at age 25)
43 4:33 mile 132 3 years of training with the last 16 months of 40 mpw with 2 workouts: 5 mile tempo and 12 minutes of intervals 4:13 1500
60 6:48 1600 158 no running but 45 minutes a day of hiking
60 5:51 mile 150 5 months of 5 mpw with 2 workouts short hard tempos some intervals plus 2 hours a day of hiking
but had not run in years.
43
Dropped 98 seconds per for a mile.
60
Dropped about 60 seconds for a mile. Off 5 months of 5 miles a week and 2 hours a day of hiking. However the 8 pounds of net weight loss accounts for a substantial portion of the improvement . Also I put on some muscle and added blood volume so I lost more than 8 pounds of fat.
Guesstimate of 45 seconds per mile off 5 months of training starting up after no running for many years.