Nope! You're welcome!
This ARTICLE will address the Conforming, generation of the PEK (Waveform Display) and also Indexing. The CFA files are necessary to Conform your audio to 32-bit floating-point for editing. The time to Conform will depend on the Duration, the original format and the speed of one's system.
As Colin says, they are necessary.
Thanks for the info.
I have a bit of disk space problem. In CS4, it will insist on generating CFA files for all media in the libraries, even though a project will use only a small set of files. Does CS5 fix this?
No. But then again, it's not something that needs "fixing". Premiere Pro converts many audio types to 32 bit floating point WAV files for internal editing. There is at least one exception, DV media. But for AAC audio, I expect this will hold true for all future versions.
Editing requires processing power, memory and disk space. It's up to end users to make they they have the hardware they need to do the job. If you need more space, buy another hard drive. (They're pretty cheap these days.)