Some of the corys i have are quite young, but the bronze seem to be spawning every few weeks, mostly at weekends when i do a frozen bloodworm feed and a water change (as you would expect). I have 6 Sterbai, 7 Pandas (which are super small) and 6 peppered to go with the 7 bronze at the moment and would love to see them all spawn at some point.
The problem i find is that all the lfs only stock juvenile fish, so you have to buy at least 6 of them to stand a chance of having mixed sex groups, which is quite an expensive way of doing it, especially if you want to have a crack at something like Adolfo's at over £15 a pop. Not forgetting that you have to wait 6+ months (guesstimate) for them to be old enough to breed.
I'd love to find someone who sells slightly older fish which you can sex, give them a good home and attempt to breed. Which im sure is no easy thing, since anyone who breeds them seems to shove their fry on eBay to sell. I'd like to just do it for a personally challenge and once/if they do breed i would end up with another massive tank to keep them in