Quote - Are there any tips or rules of thumb to getting the dynamic calculations to run faster?  I have noticed the more I use dynamic cloth that the simulations can run for 20-30 minutes, even on my 6-core Phenom II.  I leave the cloth settings pretty much stock, except sometimes drop the collision offset and depth to .5 to get better results.  I even went so far as to export a cloth item as an .obj, import it into Max, optimize the mesh from several ten thousands of vertices down to around five thousand, but that didn't have much effect.

It probably depends on several things.  I run cloth simulations with clothing that have over 30k polys and have very little problems with it. A bit slower, but not 20-30 minutes unless it's a very long animation, then it can take quite a while. And I have slower processor than you. 

I think BB already mentioned somewhere that the cloth engine doesn't take advantage of multiple cores?

One thing you can do is to check that your cloth is not set to collide with unecessary things (like feet for a shirt etc), and other objects in the scene, like hair, jewelry etc that are not needed.

Also check how the character goes from start/zero pose to final frame. Make sure the anim graph doesn't have crazy splines between the poses. Also, check that your character is taking the optimum path. Some poses I've seen have the body or hip rotated 355 degrees instead of -5, which is hardly efficient for cloth simulations. :)

You can also pre drape the cloth, if it has a lot of fabric that needs to settle. (Like wide skirts or fluffy clothes in general) Pre-drape it to your zero pose, let the fabric settle, then just export the obj, import it again and run the simulation. You may have to set constrained, decorated groups again.

But... 5k polygons shouldn't have to take very long, so something else may be wrong.  People here love screenshots, so don't hesitate posting them and describing them!