In reply to Stone_donkey:
Export as tiffs and you can reduce the image size a bit if you want because the final image otherwise can be huge!
My workflow for panoramas is:
Import images and keyword
Edit the raws for colour balance, highlights etc making sure that any adjustments are made, roughly, equally for all images in the pano
Export as tiffs
Open photoshop and build the pano.
Clean up the pano in PS and do any heavy lifting required
Save the pano as a a psd for future editing and save a tiff copy
Import the tiff into LR
Finish off editing in LR if needed, keyword, set the creating date to when the originals were taken and retire for tea and medals.