I dunno- I think "Progressive" means that the song progresses into something else, and that the music is pushing the boundaries of normal rock music. If it stays the same, then it's not really "progressing".
I'm not saying that it has to sound like 70s Yes to count as progressive - for music to evolve is good. What I mean is that, if we're going to use a genre label, there should be some criteria for the label that meaningfully define what music IS in that genre and what is not. Otherwise, we could all say we're playing baroque or something because all contemporary music has evolved and stretched the boundaries from what Bach used to do -- the "baroque" label would lose all meaning.
For my understanding of "progressive rock," those criteria would be:
1) Overt influence from classical and jazz music
2) Stress on virtuosity of individual band members (plural, not just a star soloist).
3) Frequent experimentation with unusual meters and keys across the overall body of work.
4) Length of a song determined by the logic of the piece rather than the commercial 4-minute radio slot (this may mean songs 90 seconds long or 20 minutes).
5) Extensive use of vocal harmonies rather than a single lead singer.
6) The above done with an otherwise recognizable rock band setup (electric guitars and bass, keys, drum set, etc).
I'm throwing these out as debate points, I'm curious to see if there's consensus around them or not. I suppose #5 would be the most doubtful myself, it would make exclude bands like Rush from "prog" if strictly adhered to. I kind of think of Rush as a transition band from progressive music per se to the more speed-metal stuff we hear more now. Maybe I'd say that a band should hit better than half of these for me to call it a full-fledged progressive band.
To reiterate my earlier impression, there seem to be a number of contemporary bands who are called "progressive" because they play long compositions with a lot of sixteenth notes (criteria 2, 4 and 6, so to speak, but not 1, 3 or 5). To me that's not really it. Not that they're bad bands, I'm just finicky about keeping categories distinct and meaningful.