Is pop as "disposable" as people say that it is supposed to be?

I'm not a fan of planned obsolesence, but I would guess that someone who'd answer that way would say both. Actually, I'm not sure what you're asking there.

Is a pop song that "stands the test of time" still pop?

Sure. Pop can mean a lot of things, but most things that "stand the test of time" would fall under the literal definition of pop as "popular" (i.e. people still listen to it, know it, etc.).

Furthermore, is pop's transience inherently pop?

I'm not sure that there's something built into music that makes it inherently transient. It's probably more that culture and technology are always changing, more than anything, and what was "cool" two decades ago may not be now (or as an adjunct: what was "cool" two decades ago is "cool" again because of recognition that the style has dated). Music itself, while a pretty much open system, hasn't really changed so much as the ways and whys and wherefores.

In non-pop styles of music, isn't a short shelf-life considered a bad thing?

Depends. I'd bet that a lot of the creators of what we now call "classical" music didn't think that people would know their music hundreds of years later (although how we know their music is in a pretty radically different form/context, thanks again to technology). A composer writing a piece for, say, a specific commission may not have thought that the piece had a shelf-life beyond its commission.

I'm not sure either. But then I often hear people describing pop as "candy" or being like "sugar" -- sugar is something than can give you a momentary high, and quickly bring you down lower than you started. Is there not some truth that songwriters have ways of synthesizing that effect with music?

That sounds more like booger sugar (see disco).

That's getting into some pretty wacky territory, if you ask me. The elation I can feel from hearing music is way different from, like, having too many Cocoa Puffs.

What about oldies stations then? Is what they play not pop music?

On second thought, I've never read a single U2 press release.

On third thought, Mark posted just as I wrote the above, rendering my questions completely disposable!

Exactly. And that's the attraction of the format too. But the flipside is that with the current state of radio, you see Matchbox 20 charting with "Push" two or three years after its release. It's not an attempt to fetishize it either, it's wanting to keep things safe. This has dropped pop's stature even more: It's not even flavor of the week, or however some would like to characterize it -- it's flavor of the decade. And I think that this has helped move more listeners to country and hip-hop. Those formats in particular (thinking BET, CMT and radio) have very little sense of history, or, if there is one, it is purposely ignored. While rock is still forced to worship at the altar of Rolling Stones/Pink Floyd/Led Zeppelin/Nirvana/Pearl Jam, etc., hip-hop is more like a carousel, bringing to mind Chris Rock's jest: "Here today, gone today." I mean, Skee-Lo gets no airplay on hip-hop stations, yet Seven Mary Three still gets 20 or so spins a week on rock stations.