It is my understanding that there is no set time period required to cover shorted shares. The only time a cover is mandated is when the PPS increases to a point in which the account holder hits a margin call on their account. So with a nice surge in price, they will have a margin call and will be forced to either add cash in their account cover the margin, or buy shares to close the shorted sale.
This is why you have seen a large short over the past few days. They are artificially holding it down by shorting more so they are not forced to cover. I think there will be too much demand on Monday for them to hold it down any longer. A nice surge could force a margin call and get them scrambling. That is why it is important to have a huge surge and not let them bring it right back down!
In addition you can look at http://www.otcmarkets.com/stock/RFMK/short-sales to see all the short interest. This is supposed to be reported around the 23rd of the month for the previous month end. As of the end of February, there were zero shorted shares outstanding. This is not the case anymore, but we won't have definite numbers until the 23rd and that will be for month ending March 31.
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