Is there any advantage to converting them to TIFF before importing?
If you will process such JPEG images *in several steps*, then it is resonable to do that in TIFF.
Example:
1. before stitching frames to a panorama, one may need to adjust the original frames;
2. the warping process itself;
3. blending teh warped frames;
4. post processing of the stitched pano;
5. at a later point: resizing for some presentation and sharpening
If you do these five steps in JPEG, the quality degradation associated with the JPEG encoding occurs five times.