Month-long domain auction?

[Skyyyy]

I would like to create a one-month or even two-month long domain auction. I will be contacting many people to alert them of the sale, and want to wait for companies to be able to set aside budgets. Should I announce a certain date for a 7-day auction, or should I have an auction that runs for one or two months?

Also, where would be the best place to hold the auction? Thanks!