The criteria needed is simply impossible to know. It most likely depends a great extent on factors completely outside of your control, such as how the stock market is doing, what the base interest rate has been set to by the Federral Reserve, what other uses Square might have for its capital (expansions, new research and development, etc.) and an impossibly long list of other potential factors.
It's also worth considering that Square benefits less and less every time they give yet another loan to the same business, so each subsequent loan may have much harder requirements. This if pure speculation on my part however.
I wouldn't start to worry unless you pay off your current loan completely and still haven't heard a new offer by 2 weeks after that time.
