It is recommended to gamma irradiate all test items in a single gamma run.
The staggering of gamma is when a lot is split up to be gamma irradiated on multiple dates, e.g. the components for T70 days extraction are gamma irradiated on one occasion and the components for T1 and T21 days extraction are gamma irradiated on a later occasion. This is to be able to collect and analyze all extracts on one occasion, while still fulfilling the requirement of the maximum time from gamma date to extraction initiation. This approach is allowed as long as the gamma dose received on the second occasion is comparable to the dose received on the first occasion.