It would be very difficult to develop any reliable measure for stayability. What would the standards be? How could you compare the ability of a cow to survive in Alberta versus Florida? I suppose you could come up with some figure based on the number of calves a cow produces, the frequency of production, quality of production based on offspring performance data, but there are so many variables. Some people like to speed up their generation intervals, keeping a cow only for a few years before turning the herd. Some will keep a cow until she drops. As for bulls, even more problems could arise in coming up with a meaningful stayabiliby measure. Do you keep your herd bulls for 3 years or 10? Do you breed 15 cows or 75? Do you pen breed or pasture breed? Does the bull run with the cows year round? Yes, I've seen this. In my opinion, stayability data would be far too objective to be meaningful. I would suggest buying a bull with a dam that has been a good producer for a number of years under similar conditions that you have. You also have the most valuable information on how females produce for you right on your own farm. Keep the replacements from the lines that produce the best for the longest period of time. In my opinion, it would be nearly impossible to come up with stayability standards that would be reliable on a breed wide basis.