Not Mike, but I manage and (manage to) design some electronic products myself. I believe Jason's said this too, but there are usually running changes to the build-of-materials (the “BOM”) list and minor revisions to the circuit board to either harmonize parts (use more of the same kind of part like a resistor of some physical dimension, type, and value, so you can buy more of them for cheaper), replace discontinued parts with parts that are available, or fix problems like people killing boards with static or other things that are discovered over the lifetime of a product as real people use them, or manufacturing issues that the board house may discover when they build these boards.
There may be other reasons, but those tend to be the most common ones: make it cheaper, easier to manufacture, and more durable. Features and performance tend to stay the same.
Speaking of Beethoven's Missa Solemnis, the John Eliot Gardiner recording on Archiv, while not great in sound quality, is an amazing performance, and perhaps the most technically proficient of those out there, and he totally takes advantage of his ensemble's capabilities: the big fugues have never been so thrilling. For those who don't know, Beethoven wrote this piece when he was basically deaf, so he didn't know how difficult this piece was to actually sing and perform, so it's a very hard piece to pull off without struggle, and Gardiner's is one of the few recordings that does.
Other songs that belong in the same tier as Strauss's 4 Last Songs: Mahler's Rückert-Lieder, Das Lied von der Erde, and the Liebestod from Tristan & Isolde.
