I do not think it makes ripping much / if any longer at all. The next track is ripping as the previous one is encoding so it's no issue

It only gets very slightly longer when it detects HDCD.

Don't re-rip what you have done. Just decode them later with batch converter (search the HDCD thread from December IIRC).

As George says....beware that not all HDCD even declare that they are HDCD.

Rgds,
Nick