One disk to contain them all and in the system play them. Deutsche Grammophon has released Wagner's entire Ring on a single disk. All 17 glorious hours in delicious Blu Ray sound. Karajan conducts and he is not everyone's cup of tea. Too much focus on the pretty sound they say. And in the Ring, too lightweight. But why not take advantage of being in the studio to use less than stentorian singers? After all, in the studio they no longer have to sing over a huge Wagnerian orchestra. That is a purely theatrically imposed requirement.
The long form of opera and the huge storage capacity of Blu Ray were made for each other. Here's hoping more operas appear on Blu Ray. The music is in the can. They only have to make the transfer. Excuse me. The Ride of the Valkyries calls.