Fair Isle.... Need some advice on the steek

I’m currently knitting a Fair Isle scarf in the round and want to cut it open later... So, in addition to the pattern stitches, I’ve cast on the stitches for the steek. I’m knitting the steek itself with color changes, just like I learned in class. Now my question: between the patterns, I have two rows of knit stitches without a pattern. Do I need to weave the second strand into these rows, or can I leave the strand idle? And continue knitting with just one strand... But then I’d have to work the steek in a single color. Will that hold up when I cut it?
  I’m using a virgin wool blend—
Does anyone have any advice?
Best regards, Steffi