The phrase "sustained period" refers to a significant amount of time where something continues or remains stable without interruption or decline. Full definition
Ensure you drink plenty of water and do not follow this amount of calories for sustained period of time unless advised by a medical professional. (freedieting.com)
This means I should actually hope for sustained periods of below average stock performance. (awealthofcommonsense.com)
Over sustained periods of time it is these same weather systems that lead, ultimately, to broader changes in our climate. (unfccc.int)