Chris Willman Senior Music Writer and Chief Music Critic In the four days since announcing U2’s first dates for a limited engagement at the massive new Sphere in Las Vegas, the number of shows has incrementally expanded. The mere five gigs announced on Monday got stretched to a dozen shows as of Wednesday, and now, come Thursday morning, five more were added, to make it 17 concerts going on sale this week. But if you must see this show, don’t sleep on these 17 dates under the assumption that the band will just keep adding more extensions. The extension through Nov. 4 that was announced Thursday could well represent the end of the run, since, in an earlier interview with Variety, the Edge said the band would likely be limited to six weeks in the venue — and that’s just how far these new dates take it.