Answer by Alex Hughes-Walton. Confidence votes 6. We have a Welshie/Jack Russell mix who is 15 and going strong, despite spending the first seven years of her life churning out pups in a notorious puppy mill. Aside from a few stray white hairs, she can still pass for half her age.She runs like a gazelle, dances, etc.nswer by Alex Hughes-Walton. Confidence votes 6. We have a Welshie/Jack Russell mix who is 15 and going strong, despite spending the first seven years of her life churning out pups in a notorious puppy mill. Aside from a few stray white hairs, she can still pass for half her age.