The reason I keep my audio in FLAC is because I want to keep it forever. For me, it's a question of compatibility. If you encode in a lossy format today, what will happen in the future when a new encoding format is released, or when devices stop supporting MP3? Your only choice if you wish to update will be to use lossy encoding on your lossy encoding, resulting in further degraded quality. What happens when your awesome new proprietary (e.g. Apple) device only supports AAC5 and not MP7? Encoding in lossless means that you can encode in any other lossy format at any time in the future.