Giant {{{{{{HUGS}}}}} to you Debbie! Mine are all still pretty young but I still get a sickening feeling when I think about them getting old and not able to be as active. You have obviously taken very good care of Tubby since he is still able to go on walks with you at his age. I know how much you love him and I hope there is still a lot of time for you two to share. Hopefully his body won't deteriorate any further. The thought of losing them is so heartbreaking and gut wrenching.
Give extra special kissies, hugs, and lots of snuggles to sweet Tubby.