Sales Agreement - time frame?

[Calista York]

Have been involved with a short sale in FL and all went well, closed in 3 weeks. However, now looking at a short sale in PA - which is not common here, much less experienced agents..etc. involved. Attorney wants specific language in the "Settlement to be on _____________" to state "within 30 days of lender and seller approval of short sale". I realize these types of sales can be time consuming, but is there any protection for us in stating a possible time frame to have a decision made, or allow us out of the contract? Have heard Hbsc (I think the bank) is very difficult to work with - we do have the time and would love the house for the price, but don't want to spend 6 - 8 months and still not have it be bank approved. Thanks for your input.