one per 24/hrs is not too much for most people. The mfg recommendation re. dosing is conservative and it's not uncommon for Cluster folks to use much more.

That being said, some may have a change in headache pattern. The only test is to stop using it for some days and see if your pattern returns to an earier experience.

Medical reports on this issue are inconclusive and limited.
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Headache. 2004 Jul;44(7):713-8.   

 
Subcutaneous sumatriptan induces changes in frequency pattern in cluster headache patients.

Rossi P, Lorenzo GD, Formisano R, Buzzi MG.

Objectives.-To document the relationship between the use of subcutaneous (SQ) sumatriptan (sum) and a change in frequency pattern of cluster headache (CH) in six patients. To discuss the clinical and pathophysiological implications of this observation in the context of available literature. Background.-Treatment with SQ sum may cause an increase in attack frequency of CH but data from literature are scant and controversial. Methods.-Six CH sum-naive patients (three episodic and three chronic according to the International Headache Society (IHS) criteria) are described. Results.-All six patients had very fast relief from pain and accompanying symptoms from the drug but they developed an increase in attack frequency soon after using SQ sum. IN ALL PATIENTS, THE CH RETURNED TO ITS USUAL FREQUENCY WITHIN A FEW DAYS AFTER SQ SUM WAS WITHDRAWN OR REPLACED WITH OTHER DRUGS. Five patients were not taking any prophylactic treatment and SQ sum was the only drug prescribed to treat their headache.

CONCLUSIONS.-PHYSICIANS SHOULD RECOGNIZE THE POSSIBILITY THAT TREATMENT OF CH WITH SQ SUM MAY BE ASSOCIATED WITH AN INCREASED FREQUENCY OF HEADACHE ATTACKS.

PMID: 15209695 [PubMed]

{Note from BJ: Review of PubMed in 1/11 found no citations with this type of data in the last 10-years. The absence of newer reports suggests that experience of recent date is not stimulating much attention on this topic. In view of this reports comments about quick return to the former headache pattern, it appears such changes in frequency is not a significant issue.}