Seriously, it takes seconds to do the transform either way on around four minute songs. Lemme grab some stats....

Hmmm. Seems to take longer than I remember. I compressed Pink Floyd's Money (6:22) in about 1 minute. It decompresses in about 30 seconds. I could swear that I got faster times before. It's still well faster than encoding mp3s, so as long as you do it via a pipe, it'll be just as fast. (Keep in mind I'm doing this on a P2 333.)

Regardless, unless you're listening to the WAV files on your home machine, FLAC will save you space, which is still pertinent to your quest for more drive space. And if you use WinAMP to listen to your WAVs, there's a plugin that works perfectly for FLAC.