Can you merge multiple panorama files into 1 larger panorama file?

I've been pleased with LR's panorama merge feature combining as many as 15 verticals into one long horizontal panorama. One important factor is to have plenty of overlap, 30-50% both horizontally and vertically is important. Have you tried using the lens correction function on each image before trying the merge?

Creating large panoramas can be a challenge for sure. I have had a few successes have a lot of failures. I have not had any successes trying to combine smaller panoramas to create a larger panorama. But then, I'm not a very skilled photographer either. I use a Nikon D7100, which is a APS-C camera, and the largest panorama I have been able to create consisted of 21 NEF files. Those files were arranged in three horizontal rows of seven images, and were taken with a 35mm lens, which is a "normal" lens on that camera. I started the sequence in the upper left-hand corner, then I photographed downward for two shots, then went over and back up two shots and so forth until I completed the image. The normal focal length seemed to work well, and Lightroom seemed to stitch the image without a lot of distortion. I think the challenge with trying to combine three different panoramas would be to have the perspective or perceived focal length match precisely so the Lightroom or Photoshop could accurately align the different images to make a good panorama. At least that has been my experience. It's just easier to try to do it in the camera. Using a moderate focal length, like a normal perspective, seems to have worked well for me.