You are wonderful! 40 dogs in 36 years - wow! My husband and I take in old rescue dogs as well. We’ve only had three. They are the sweetest things. I lost one of them a year ago - only had her two years. I thought I’d have her longer and was shocked when we lost her. She was eleven so I shouldn’t have been surprised.
I can’t even look at the photo of the old dog. She looks so tired, poor thing. We don’t have “Lassie” endings anymore, I guess.
“....only had her two years”
That’s about it with the older rescues. If you have them longer than that, count the blessings.