About compression keyframes:
Compression keyframes are different from the keyframes placed in the Premiere Timeline window. Compression keyframes are automatically placed during export at regular intervals in the movie. During compression, they are stored as complete frames. The frames between the keyframes, called intermediate frames, are compared to the previous frame and only the changed data is stored. This process can greatly reduce file size, depending on the spacing of the keyframes. Fewer keyframes and more intermediate frames result in smaller file sizes, but produce lower-quality images and playback. More keyframes and fewer intermediate frames result in significantly larger file sizes, but produce higher-quality images and playback.
This is for Adobe Premiere 6 LE; I'm pretty sure different versions would have different help files. When you export the video there should be a function for editing size/quality/etc
P.S. I was going to send this in a PM Senor, but your inbox is maxed out right now