I think you didn't touch on an important side of the issue here. While MP3 is the most popular format now in the future it may fall completely by the wayside and you might have a device that doesn't support it or simply want the advantages of another format. By storing all of your music using a lossy codec and getting rid of the reference media you've lost your ability to re-encode it without reducing the quality further. A lossless codec such as FLAC does take more storage space but it also allows you to re-encode to something else without any quality loss. Personally I'd much rather take the space hit to store my music as FLAC on my home server (Running out of space with 6TB would take a LOT of music). Encoding from FLAC to MP3 (or another format of choice) is fast enough on a modern system that I'll simply re-encode the playlist of choice and then sync that to my phone where space actually does matter. If you're going full MP3 I would reconsider getting rid of the physical CDs, they may be fine for listening (depending who you ask of course) but it is not a good archival format.