We adopted Buddy Guy in 2006. Best guess, around 3 or 4 years old. He is super smart and the best-behaved rescue dog we have ever had. His love of life (aside from his new forever family) was to play ball every day like the Energizer Bunny!
A couple of years ago he started to slow down and the vet put him on an anti-inflammatory and some pain meds. It seemed to help but, over time, he went from walking (and enjoying) 1 brisk mile a day, to having a hard time with a 1/2 mile and finally, 2 blocks, before his back legs started to give out.