Largemouth Bass on the Sassafras

Type: Nontidal
Region: Eastern
Location: Sassafras River

I recently caught a largemouth bass weighing 7lbs 12 oz and was 22 1/4" long on the Sassafras River. I would like to know approximately how old the fish was? I am thinking it had to be at least 15 years old. I have been fishing that river for 50 years and that is the largest I have caught there. I admired it, took some pictures and released her unharmed hopefully to grow bigger next year.