I only make by four cup batches and find that five days with scoby intact is my preferance, and then I add my flavor building and it parks for another 1-4 days on counter, then I transfer to bottles and tightly cap or just tighten the lid on counter container and refrigerate. My drinks are nicely carbonated.
I do believe the volume of your ferment will be indicative of number of ferment days, along with temperature. Taste can be impacted by type of tea used.
Just removed the scoby from a four cup batch which used a tea made from 2 restaurant size jasmine green teabags and two orange pekoe, 2 tbsp sugar per cup of...68f on counter...delicious as is but I can never resist adding fruit or juice, etc.
Motto: quel che sara sara