It occurs to me that a detailed response to your response might be useful to other users. I am creating a slide show composed of images with music and narration about 30 minutes long. I selected all the pix first and assembled them in the sequence. Now, I am working to match the narration to the images.
Adding Narration.I never noticed the "Add to Sequence" option and was using the method of dragging the narration clips to the timeline. I thought Photostage would just drop in the entire file and didn't realize you have to make a selection first, so I ended up having to do a very tedious job of expanding the selection on the time line. So that issue is solved.
Adjusting image length. I now notice that the image I couldn't alter the length of is between two images I have already lengthened manually, so there may be an automatic control operating. To be clear, the image on the timeline still displays the old time, but when I click on the little button at the bottom of the image it displays the actual time I have set for it.