btw, if you're curious why I'm asking, it's because of what I read in Adobe's Help file:
"Before rendering, put all of your source footage files on a local disk—not the one that the application runs from. A good way to do this is with the Collect Files command."
AE CS4 Help was written before SSDs became popular so I wonder how much would change if it were amended now.
Anyway, bringing the source files together onto the SSD seems like a good idea to me. But I'll test it - render the same project with the assets imported onto the SSD and also with them sitting on a mechanical disk.
The general guidance hasn't changed:
Put your source files in the place where they can be accessed most quickly.
If you're curious about which setup is optimal for you, I encourage you to run a couple of simple tests and find out.
thank Todd - that's what I'll do...