One very important consideration in your situation is to determine if you have moisture sensitive components on these boards.
If you have any device classified level 3 or higher then you have a very high level of risk associated with moisture sensitivity. A level 3 component has a maximum floor life of one week prior to reflow once the components are removed from their dry bags. If you run these boards through an additional reflow without baking them first this may result in internal cracks and delaminations, maybe even popcorning. These are insidious latent defects that can pass electrical test but may result in early life failures in the field.
The default baking conditions are 48 hours at 125C. You may obtain more details by consulting the joint IPC/JEDEC standard J-STD-033 : Standard for Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices. This document can be downloaded for free at http://www.jedec.org
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