Once you reserve a room for 7 nights at exactly 11-months out, no one else can reserve that room for any dates at all that are 11 months out, or later, until 11-months out from your designated departure date. Thus, if you want to add nights, you could do so by adding one night daily after you reserve, or you could just wait up to six days and add all the extra nights at the same time. It just needs to be done at least one day before 11-months out from your designated departure date. And you do not need to do that addition at exactly 8 a.m. You just need to do it at any time during the particular day you make the change.
The one risk to waiting and not doing it daily is the possibility that a room or rooms in your booking category gets designated for closure (for maintenance or refurb) for dates beginning after your initial 7-night reservation because that would take a room (or rooms) out of service and the remaining rooms for those extra dates that you want may be filled by others reserving after you reserved. That is probably an extremely low risk for waiting a few nights before doing the addition of dates to your reservation rather than adding a night daily, but one cannot definitely conclude it is necessarily a zero risk.