Yes true. Only the average viewer probably doesn’t look there 
It depends on the segment. You can learn more in the NSSA guide for segmenters - https://nssacademy.weebly.com/segmenting-guide.html#extensionsgaps
But in short, if you can make a 1 sec “buffer” after the sentence ends and there is enough space after (min. 0.6 secs), you do so. If not, you connect it to the next segment. Your segments also shouldn’t be too short ( >1 sec). You want it to be readable. These are the standard rules, but some people do deviate from it sometimes (f.e. a 0.9 sec segment with the words “Yes” or “No” in it or a slightly longer buffer).