Jim~
I think that, as a breeder, is a tough call. I can tell you a little something that I have personally seen, though. My next door neighbors are in their late 80's and you would NEVER know it!! When we first moved in here, I talked to them several times out in the yard....while they were barbequeing or doing their yard work or just out for their usual walks. My husband and I assumed that Bob and Myrt were in their 60's....because they TRULY look it and are VERY active people!!!! It wasn't until Myrt said something about sharing her birthday month with my son but that she was (at that time) 82 years older than him. I had one of those moments where you continue on with the conversation and then, WHAM!! It hits you 5 minutes later what she just said.
I couldn't get over it! We have lived here amost 3 years now and they still go out for a couple of walks a day (no matter what they weather is....unless it is too cold, obviously) and they are ALWAYS working in the yard and Bob is always waving to me while he is grilling.
About year or so ago, they went to the humane society and adopted Julie (their sweet Beagle). At the time, I told my husband that I didn't know what I thought about that because of their age. But ya know, they have had less colds, Pneumonia, flu(s), ear infections than my family....in fact, I do not know of them having any of these above since we have lived here!! We are more sick than they have been with all of those things that I mentioned and we range in age from 4-40. If something does happen to them, I can tell ya, that precious Julie has lived this part of her life VERY, I mean VERY spoiled by Bob and Myrt!!!!
I can't tell ya for sure what I would do in your situation, but I do think that if your heart is telling you that this would be a wonderfully loving home, then these people are worth considering.
Tammy