There are very different viewpoints on this forum and to each his/her own.
I have raised animals all my life, we are in the livestock business, it has been my experience that healthy animals are much happier animals, they convert feed better, and live more comfortable lives. Animals that are not 'thrifty' are culled out, rather than extensively treated.
Couldn't agree more, but I think you're misunderstanding my setup perhaps. Just because I work to save damaged or ill animals doesn't mean I go on to breed them; I'm very choosy about which animals go on to breed. Predisposition to scaly leg mite is enough for me to cull a bird, for example. Most people don't even know there is a predisposition to it, but I've identified certain family lines who are reliably susceptible to it and others effectively immune to it. Doesn't mean I will let them languish with just food, water, and isolation for treatment until they either make some kind of recovery or are culled for it, but also doesn't mean I breed them once I've treated them, if they've shown extreme susceptibility.
I value the learning process and information gained, as I'm very interested in the medical aspects of keeping animals, not just commercial. Not right for everyone but invaluable for people like me. If my values were different I might be doing the same as you, but it's really not an option for me.
Over the years, this has produced a high quality healthy herd. It is the same practice I apply to my small flock. Frankly only having one sick bird in 7 years, I think it is a pretty healthy flock.
It probably is a pretty healthy flock, but different strokes for different folks and all that... Some people would buy specifically from people like you, and not me, whereas I wouldn't buy from people like you, due to their immune systems lacking exposure to common diseases. I value them having that proven resistance rather than only being able to guess as to whether I'm breeding highly susceptible animals which are remaining healthy only because they're in an over-sanitized/isolated environment, or otherwise.
However your setup, going from historical precedent, can work for the rest of your lifetime, so if it works for you that's great. Possibly not so great for the genetic legacies of those birds though, as they're 'out of circulation' and being reintroduced to the world in general, or having outsiders introduced in order to bring in new blood, is potentially fatal to the entire lot of them.
That's my personal reasons against doing the same, in a nutshell, but some people have successfully kept linebred/ inbred lines for decades, if you're a good breeder or spend the time learning it is apparently workable, not that it appears able to be perpetually sustained. All depends on what you want your flock for I guess; some people with very rare genetics don't have almost any other options.
However, all the different ways of doing things make coming to this forum interesting.
Mrs K