The only study I know that touched on lifespan was just notes on a study about mortality over time and causes using autopsy. There was a graph that showed that most of the females lived to about two years and a couple of the males had hung in there until around three years.
It seems like it wouldn't be possible to identify which are the longest lived among a group of quail before they would be long out of their breeding prime. You'd need to produce offspring from all of the birds and keep track (several generations) of the offspring during the lifespan of the original birds in order to know which of the next generations had received the "long life" tendency. You'd basically need to establish lines for each of your test hens. That would require individual cages for the hens and either roo-hen pairs (not a good ratio for coturnix) or periodic controlled mating. You'd also need to figure out which of your males is carrying the "long life" tendency.
What would be the appeal of having coturnix with a long lifespan anyway? More desirable (and achievable) goals might be: temperament, weight gain, body type, early sexing, early onset of lay, egg size, egg frequency, or extended period of lay/fertility. Apparently, coturnix had been bred in Japan as songbirds as well, but those lines were lost during World War II. I'd really like to know what they sounded like and whether it would be possible to breed for vocalizations.
