As I understand it, yes breba always on old wood, main crop on new. Main crop apppearance has a lot to due with your zone, with the weather and of course tree maturity and variety. Actually with all those variables a hard question to answer. In your zone 8 I would expect you should be seeing main crops on most everything by now. Of course the presence of breba may also slow down main croop production, another variable. If you're not seeing main crop in your zone it is likely due to young trees? Breba and main crop will attain a mature size and just sit there doing nothing for a long time and that time depends on those variables, especially temps. But always longer than you want to wait, then boom, they swell up in a couple days and you eat with a big smile.