I can not remember how long ago I answered a similar question regarding SS. The same as REO, The tempo is generally decided by the lender. The difference between REO and SS is lender is the seller in REO but lender is just a contigency approver in SS. That means in REO, lender must response everything under the contract whatever yes or no, but in SS, lender can keep slient there or delay the response. Of cause, in REO, lender prefer to use counter offer to rewrite buyer's CAR purchase agreement and make the terms to benefit lender. In SS, do not think that buyer or agents hav elegal right to push lender to make decision. That is just a contigentcy. Remember, on buyer's side, buyer has no right to ask buyer's lender to approv buyer's loan.
Some of lenders in CA prefer REO not SS. They have some internal issues. 30 days, 60 days, 90 days are popular but do not let your clients misunderstand that you gurantee it. Otherwise it is going to be dangerous. Do not put yourself in hot water.