" Hydrangeas can be brought inside over winter. They may not provide blooms, but they will remain alive. They won't enter a dormancy period if not left in the cold. Hydrangeas do not need dormancy in order to bloom in the spring and summer. " from Plant Addicts.

ALL deciduous shrubs that do not originate from a tropical climate (if there are any) require a period of dormancy!! If prevented from entering dormancy (kept indoors in too warm conditions), they might bloom the first season after but I would not put money on it :-) Read up on vernalization. Do not believe everything written online!!

The cuttings will typically go dormant once soil temperatures and shorter days arrive so let them drop leaves and go dormant as they wish. No need to keep them awake. The roots may grow a little during this slumber in the garage/etc though.