At least 10 years, but de facto many generations, as old bucks get culled and there are at least several generations between old and new. Not sure if I explained it right...
Re: selection, usually the biggest of the litter is selected for both buck and doe replacement. Also does have basically a single chance, meaning if they are bred seemingly successfully and they don't give birth, they get culled and are replaced by the biggest doe of the next generation.
And you are right, you need organization 🤣 What is working here is having a ledger with numbered cages and going down you write when the doe was bred, when it's due and how many she birthed and when she should be bred again. So it's easy to see the most important things daily. When should you breed, when is birth expected, how each doe performs in time.
I'm sure an app could help, but a notebook could help as well 😉
RE: Cinco de Mayo 2021: Pork, Peaches, and Sweet Torture