It shouldn’t. Yes, it always does.
Offline and online editing HD should closely resemble regular video editing or film editing in case of 23.98p production. HD may take longer. A typical HD production for TV or cable will use multiple tape formats and multiple frame rates. Also, since you’re dealing with a larger image it will take longer to render effects. This is the area where a very fast high end editing/compositing box outperforms less expensive NLEs.
In some cases the amount of time needed for HD editing can be comparable to the SD counterpart.