I've moved up to 400 / 25 minutes. I've found there's ZERO detriment in cooking for longer but things go bad when under cooked or over temp.
Under time you get soft coating and over temp you get brittle coating. Keep that temp at 400 and you can cook for hours without any negative impact. The key is getting the temp perfect and keeping it perfect and cooking it long enough to fully cure, whatever time that be based on the number of bullets in your bake and the size of bullets.
I've recently switched to loading up my oven. I used to do just 1 tray at a time. I now stack the trays 3 high. I am baking over 1k 9mm's at a time which is a lot of lead in the oven. By moving to 25 minutes, and sometimes even 30, I know for certain I'm getting everything fully up to temp and for long enough. All my smash tests come out perfect and I get zero leading in my barrels.
I've also recovered a few bullets down range that missed their targets and you could literally resize them and load them back up. They look perfect.