The goal of any breeding program, whether with livestock, dogs, flowers or anything else is to improve upon the generation before. If you don't improve you try again, perhaps from a different angle. If something works, you have moved ahead. Then comes the task of deciding :Should I move forward with the offspring and that offspring in turn is replaced by its offspring? This would be the quickest way, in a perfect world, to move ahead with any goal or breeding program.
What if the dam is a real producer and you like the offspring, they are better than the dam, but want to take her a different route? Is it ok to do so? What if you don't get better offspring then? I think about this quite often now. All three litters I've had...the pups are better than their dams. Do I need to breed them again if I already have improvements on them? What if I want to go to a different line to bring in something different?
In my cattle I have one cow that I kept and bred for 9 calves. Each year I bred her to a different bull line, hoping to bring in VERY specific things from each line to blend with my cow genetics of this particular line. I had no problem repeating a breeding in the cow one year as you only get one calf per year, and I always want heifers as I can use frozen semen on bulls that are from all over the world.
In dogs I feel its a bit different. If I retain two puppies from a litter, I can go different directions with the pups, or I can go the same direction as each pup has different things I like about them. Do I move forward with the pups and hope I get something useful out the pups 'in a perfect world'? Or do I breed the dam again and breed her to a different line, bringing in something very specific that I didn't get in this breeding (or I want more of)?
Its just food for thought. I know everyone in the same situation would do it differently and that's ok. Just trying to think out loud. 4 is easier to manage than 6, but I'd hate to lose the opportunity to use the dams again if I was really pleased with the outcome.
This being on the mend stinks! Too much free time to think about other stuff! >:)