There's no official ruling, but calls to the Helpline over several years have yielded a consistent answer: If there has been a break of more than 90 days, the next SAR is not a "continuation" SAR.
Regardless it would be prudent to summarize the preceding activity at the beginning of the narrative and provide the DCN of the final chapter in the earlier series.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.