I have an 87-disc Complete Beethoven box set. Every disc has the same paper sleeve, so different cover art was out of the question. I can't remember if the disc titles came in as "Complete Beethoven - Disc 1" etc, but I think they did. I created a "Beethoven Box" genre so I could group them easily without giving them all the same title but different disc numbers. After a while I realized this made it very difficult to find particular pieces, so I selected tracks within the same opus and changed the album name to the opus name (eg "Sonata for Violin and Piano No. 9 in a Major (Kreutzer), Op. 47"). This produced many more than 87 "albums", but made finding and listening much easier - and they're still grouped in the "Beethoven Box" genre.
I also bought the Marias Callas remastered studio recordings box. In this case each disc had its own cover art, so I did nothing special to group them, other than making sure one of the artist names was Maria Callas. Using this system I see other Callas discs I have that aren't part of the box set, but it wasn't important to me to break out the set. If I had wanted to do that I would have created another genre "Callas Box Set" or something like that. Since I ripped them in order, sorting by date imported preserves the sequence of the box set.
I don't use disc number for pop music sets because normally I want to play one disc from the set, but not the entire set. In that case I'll put the disc number in the album name. I do use disc number for things like operas or symphonies that I want to play from start to finish with a single click.