I answered this on your other post, ZZ, but here it is again
In Las Vegas and Henderson, usually there is a short sale addendum attached to the purchase contract which specifies that the buyer must stay in the contract for a minimum length of time while waiting for a response from the bank. The addendum specifies time periods from 45 days to 90 days. After that, the buyer is able to cancel the contract with no penalty if a response has not yet been received from the bank. You should check your contract to see if a short sale addendum was included and what the time period states. You should also ask your real estate agent that prepared the contract to help you with this.
Otherwise, there is no set time frame where the bank must respond. I have literally seen short sales take anywhere from 30 days (that was with a very small bank) to over 2 years. You can read more about why here:
Hope this helps!
Berkshire Hathaway HomeServices
The Tonnesen Team - with over 30 years of experience helping families call Las Vegas "home!"