I can tell you that other agents I have talked to have had short sales completed in as little as 75 days and other agents have been waiting 9 months. It all depends on the lender and the investor(s) that hold the note.
Here is an example that may or may not be true - this is just my thought process.
Susan let's say that you are wealthy (25 million) and decide to take 5 million dollars and invest it in real estate. You become in a sense "the bank" and loan people money to purchase homes. To make it simple let's say you loaned $500,000 to 10 different people to buy 10 different homes. Now let's say that one of those homeowners gets behind on payments and is trying to do a short sale. The home that was worth $500,000 is now worth $350,000 because the owner bought at the peak of the market. A short sale contract comes in at $300,000. You were getting a nice 7% return as an investor on the $500,000 but now you are getting 0% and they are asking you to loose $200,000+ of your money. Do you 1) approve the short sale and cut your loses 2) disapprove the short sale and pay additional fees to foreclose and then after it forecloses A) sit on the property until values come back up or B) sell it for what the market will bear and cut your loses? This is a possible scenario that investors are facing and that is why the process could take a long time.
I have looked at a few SOLD short sales and found out that some of them are obtained at below market value and some of them are obtained at market value.
I hope this helps.