@Nick Scalero I guess in the case of multiple offers as you are doing, you would need to put in the contingency you suggested about other offers being voided after one is accepted. Or, you would need to be prepared to close on all.
@Wayne Brooks For one of the short sale offers, the time for seller's acceptance was left blank per my attorney's advice because he said we did not know when the seller would accept. Now, there was a short sale addendum that required the seller to get release from secured parties (e.g., the bank) within 90 days. I did not have a chance to ask my attorney, but I figured the offer would expired after 90 days if we did not hear anything.
@Kim Knox the offer had inspection and mortgage contingencies that specified a certain number of days after short sale approval. However, I do not think there was any limit on how long the short sale approval could take other than the addendum that required secured party release within 90 days.