In that time we've had many litters of puppies, usually trading them with neighbors to improve the local landrace and pass around some of the best traits. There's a steady input of "dumped purebeed" in the local mutts, they never survive long unless rescued.
"Pure" breeds are useful in being controlled and defined parameters to breed from; hybrids are the best "working" dogs however. IMO.
Our greatest successes have been with hunting hounds (bluetick coonhound or great danes) x "herding dogs" of some spread. The border collie x Bluetick cross produces some great dogs but there's a high proportion of psychopaths; expect 1:20 or so to be one of those puppies you just cant do anything with without insane effort. Bluetick x Catahoula are more mentally stable but likely to fall to the "merle on merle" cillia based health issues. (Digestive trouble and/or hearing issues)
Great danes x collie were robust, intelligent, big dogs that avoided almost all the inhertibale issues of the parent lines; but that's a cross you don't want to undertake raising without significant time. They're as bright as a small child and they feel they need a job: furthermore if you're not the boss, they feel they have to be. Of 4 litters (all large, hounds are profligate) we got 2 willful and bright enough I'd call them "psycho pups". Bad news at that size and vitality. Great for a herd dog, but only if you don't care about having input into how the herd is run.