When you fill in the "Need Request" form there is an urgency [date] tab which you can use to indicate to the group the time you have available for your request (i.e. users must weigh-in by this date). An urgent need might require a three day answer request whereas something that might be an important need but not crucial time-wise you could give two weeks to. You have the option to select between 48 hrs and one month as your deadline for response.
A word of caution, critical needs that are given a short weigh-in time may not receive the kind of support you are hoping for simply because people do not have the ability to always respond very quickly. Make sure you communicate urgency accurately to ensure that you get quick responses when you need them and don't try rush the process unnecessarily.