I pray it over nine days.
From EWTN:
*A novena is a nine-day period of private or public prayer to obtain special graces, to implore special favors, or to make special petitions. (Novena is derived from the Latin “novem”, meaning nine.) As the definition suggests, the novena has always had more of a sense of urgency and neediness.
*
Having noted that, there are novenas that may be prayed 9 consecutive hours, for example, the Infant of Prague “emergency” novena…but since novenas are a private devotion, for the most part. you may pray them as you wish.
I would stick to the 9 days. It allows more time fro reflection and inspiration. That’s just my personal opinion.
God bless.