I abandoned the manufacturers' disc numbers by my second year in business, inspired by using a Sony 300 disc player at the time. Slots in the player were 001 through 300, so I just relabeled my discs 001, 002, etc with a marker, and began using song numbers in my book: 001-01 (for disc 1 track 1) 001-02 (for track 2) etc, but I always pre-appended the manufacturer initials to my disc/slot #. Thus a line in my book might be "SC-102-04 |All Star|Smash Mouth" meaning the Sound Choice version, on my 102nd disc, track 4. Input 10204 on the disc player, and up came that song. In the rare instances where there'd be 2 versions from the same manufacturer, I just typed the difference into the title so anyone who cared would know which is which.
Just stuck with 3-digit disc numbers after I went computer. I didn't have to name any files. Ripping disc 421 I'd use "421" as the root name, the ripper would name each track 421-01.cdg, 421-02.cdg, etc. so the results corresponded to the books I already had. Now I just input the song # on a numeric keypad to launch songs on the computer.
So along came downloads, and I just kept making up 3-digit disc numbers, but now a "virtual disc" holds 99 tracks (could be more, but track #'s are formatted as 2-digit numbers in my master data base). My first "virtual disc" was 650, so my first 99 downloads became 650-01 thru 650-99. Then I started my next disc as 651. Now I've got 19 virtual discs of 99 songs each.
Now this would have gotten ugly, but it didn't because I wrote my own Re-Namer Program (hey, that's the the subject of this thread!) to do all the work for me. My downloads accumulate in a folder, I periodically unleash the Re-Namer on that folder, and it assigns the song numbers for me, renames the files for me, and exports the lines for my song book with title, artist, manufacturer abbreviation, and my song number. My book is updated, and I haven't had to type a line.
Of course I spent 100 hours writing the program... I could probably type a few thousand entries manually in the same amount of time -- but what fun would that be?