Question about sold out staking pools

I’ve been on Binance doing some staking the last couple months. I’ve been able to get into a couple 7 and 15 day pools but once they are done I only have 30,60 and 90 day options. 90 has always been sold out. I’ve signed up for emails and telegram messages on a 3rd party place for when they aren’t sold out or for when a new pool is added. Just wondering if anyone knows how frequent these are added? I’m fine waiting a couple days but if it ends up being a week or a month I would be better off just putting it into a lower percent pool and starting today. Thanks and sorry in advance if this has been covered.