Because I thought it would be cruel to not say this, my white broad breasted female is a year and a half old and is perfectly healthy. She has no issues and never has, lays eggs often and is healthy as can be.
there is nothing cruel about keeping that turkey..
I once kept a few Cornish/X hens. they acted normal and laid eggs for us for a long time..
I suspect that the extra energy goes into the egg laying instead of putting on pounds..
when we raise cornish/X for meat, we do not pen them up. they go free ranging right along with all the rest of whatever birds we have. never have any drop over from heart failure, and out of hundreds of them, very rarely have any with bowed legs.. the exercise keeps them healthy..