At the current state, players can withdraw per 10 days. In a certain percentage, players are actually withdrawing day-by-day since "per 10 days" is based from previous withdrawal. If players 1-10 withdrew from 1st to 10th day of the month, that's withdrawal everyday and next withdrawal may be done by players 1-10 from 11th to 20th of the month.
By having withdrawals twice per month on specific days (e.g., 10th and 20th) rather than per 10 days from previous withdrawal, we can allow the price to 1) take a breather by preventing dumps everyday and 2) for prices to move higher [in a better pace] assuming that players are doing evolution or breeding [and other upcoming burning mechanisms] outside withdrawal dates.
This may seem as a disadvantage to scholars due to the controlled withdrawal, but it actually works for scholars [who are main dumpers of UMY] and other investors as it allows them to maximize the exchange rate.
We do it twice per month instead of once a month to avoid big declines. We avoid thrice a month to have a long breather for prices during, for example January 20 to February 10 (i.e., allowing a longer time for prices to recover before another dumping happens).