Sounds OK. My laptop (latest macbookpro, unpluggled from power) takes around 10 sec. per frame to export.
500 frames * 10 sec: ~ 1h 20 min.
Once done editing, you can try to delete all the previews, select the 2010 raw engine, re-generate full-size previews (or standard size) and optimize your catalog upon exit.
Make sure your drives are not in degraded state (poor perf. is often is symptoms).
I believe this post may have been better targeted at the Lightroom Forum proper. And no, I'm not the forum moderator, but yes - I've made this sort of mistake more than once myself...
Thanks for your responces. I guess this is pretty normal.
Yes - rendering raws from scratch takes a long time on any machine using any software - at least a few seconds each if there are few adjustments, fast ("bugless") software, and fast hardware... More likely several seconds+ on the average. If you re-export much, consider folding changes into a tif or jpeg which will then render much faster. Also, if the first ones render fast but the latter ones render slow, you're software has a bug that probably includes a memory leak - consider dividing the exports into smaller chunks and restart Lightroom in between until the bugs are fixed.