Have these fish even been conditioned?
I hope those aren't just pet store CTs of unknown ages and breeding. If they are, you're in for some trouble, as most pet store males are past their prime, which dramatically increases the chance of defective offspring... I also hope you read the pinned info, know who you'll be selling the babies to, have a spawn tank, and are fully prepared for breeding. Honestly, the other day you were asking if you could throw two females together, and today you are wondering how long bubblenesting takes, which makes me think you don't know much about bettas. It would be best to first perfect basic betta care before plunging into breeding, which takes an immense amount of time, money, space, and effort... and when done incorrectly, will result in some very dead fish.