When I was on staff at Colonial Williamsburg, the minimum lead time for loans was 6 months; it may be longer now. This was to allow time for conservators to examine the requested object to determine whether it was in condition to travel and, if so, determine whether there was any conservation that needed to be performed prior to the loan; receive the facility report from the requesting museum/historic site; complete the loan documents, including proof of insurance from the borrowing organization; and then arrange for transport, including crating.
When I was on staff at the Jamestown-Yorktown Foundation and working on requesting loans for both the permanent exhibit and a temporary exhibit, loan requests had to be made at least 6 months ahead and, in some instances (especially international loans), over a year in advance. On the other hand, we did borrow objects from Colonial Williamsburg, but since that is a close-by institution with whom JYF has a good relationship, some of what CW required from other organizations was waived because of the proximity (transportation of the requested objects was by JYF van and personnel, rather than by a fine arts carrier).
I would say that 30 days barely gives you enough time to make sure the requested object is in good shape to loan, vet the requesting institution, get a facility report to make sure that the environmental conditions for the object you're loaning are what you want (e.g., temperature and humidity controls for uniforms or trading cards), verify insurance, and then arrange shipping, since shipping with a fine arts courier can take some time to arrange and even if you should choose to use another shipper, pack the object safely.
Hope this is helpful information
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Martha Katz-Hyman
Independent Curator
Newport News, VA
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