Billy once said that he strongly believes in the "three years between albums"-principle (although he hasn't always followed that rule himself: MCIS '95, Adore '97).
It's obvious that songs like 99 floors and all the rest were written because Billy HAD to write them, he had kind of promised the fans that he would give them insight into his process of creation during these residency shows... He probably forced these songs out of himself, and whether they are good or not doesn't really matter to him, he's not going to re-use them anyway (I think).
And no, Rivers Cuomo, technically speaking you can't call these songs 'b-sides'. A b-side is a song that was originally written for an album, but did not make it onto that album because there were other songs that sounded better.
Not that any of this really matters, I would also love to see a new album very soon (yes, an acoustic album would be very nice! I have never heard anything acoustic by the pumpkins that I didn't like, I think they are at their best when they play acoustic). But I don't think that's gonna happen really soon. But hey, I'm not tired of Zeitgeist yet!
