If I'm not putting a stitch pattern in the sock, I rib the whole cuff. Most cuff's with a pattern are nice and snug with a few inches of ribbing at the top. At least that's how I see it
And BTW I'm now as we speak working on some fixation sock's. I'm doing both at the same time on two different set's of circular needle's. I'm ribbing the complete cuffs, about 6 inches. That's the part that takes the longest for me.