As a private devotion, it is your commitment to make however you wish to do so. Nine is just the number of repetitions (hence the name “novena”). It is no less and no more a “novena” if it is faithfully and sincerely done in nine minutes, nine hours, nine days, nine weeks, nine months, or nine years. Right now, I’m in the middle of two novenas being done once a day over nine days – one for the Immaculate Conception which will end Wednesday and one for St. Lucy which I just began in advance of her feast day.