Often times, I end up using mp3's in my projects, and I believe PPro conforms them to the project settings higher quality. Therefore, I haven;t really noticed a difference between using an mp3 vs an uncompressed wav track from a cd. However, should this practice be avoided? Should I only use songs in uncompressed wav format?

Premiere traditionally hates mp3s. It's more stable if you use wavs. Plus the audio quality should be better with wavs. (Of course, once the file has been compressed to mp3, converting back to wav doesn't add back the quality that was lost.)

+1. Wave files at 48kHz, 16 bit is the "native" audio format for PP. In complex or long projects, I'll render out the audio track to a single file and then drop it on the timeline over the original. It saves me from issues when it comes to the final output.

I've been using Easy CD-DA Extractor for ripping CDs to mp3s for over a decade and it's flawless. No bad rips in over 400 CDs. None. Nada. It will also convert audio files from almost anything to almost anything else and there's no need to open the file and view a waveform. Just drop as many files as you want into the queue and let it eat. US$25 well spent those many years ago.

Use this, or something like it to convert your files before you import them to PP to eliminate potential problems.

DBpoweramp is a great utility for converting mp3 to 48khz wave files.