CS4

I capture HDV, import HDV M2T files then edit in HDV. I get the movie complete and go to export it to tape. Render so no red pre-renders are there.
I connect an HDV camcorder and go to export to tape.

A box comes up to transcode and record, so the camera has to wait before it transcodes to HDV before it outputs to tape.
Anyone know of particular setting that I've not done - the files are already HDV, so why a need to transcode?

Because you edited GOP/MPEG material.

It is re-encoding your entire sequence into a single MPEG2 stream before it writes that file back to the tape. That is what takes so long. I would never write finished work back to HDV tape. There is a major quality hit and it takes forever. Find a different way to deliver your finished work.