You got some great advice from Todd and Dave. What can add is that if you have certain parts of the video where nothing happens on the screen (e.g. the presenter talks over a interface) try to think of a way to animate a simple schematic of what the voice over talks about. Even a simple animation of keywords from the voice over will do.
Here’s an example: https://ae.tutsplus.com/tutorials/workflow/aetuts-plug-in-review-shapeshifter-ae-vs-invigorator-pro/?search_index=3
AE CS5.5 does not make use of Cuda- Premiere does. However, CS6 and up, it’s a different issue. Having an Nvidia card will benefit AE.
So if you plan to upgrade soon to CS6, then it’s worth upgrading, if not, get more RAM, that’s what makes AE faster.
As far as optimizing: https://forums.adobe.com/thread/543440