That's just one person's opinion. What's annoying about a promotion for one of the station's major events, even though it's in the rear-view mirror? I would think (and agree) that the station sees it more as a "thank you" not only to the listeners who attended, but to the advertisers and personnel involved with putting the show on. I've heard Hot 97 in New York air similar "post-show" promos for their popular "Summer Jam". If anything, it could give listeners incentive to grab tickets for the following year's event.
Was this year's "Hot Jam" sold out? If so, I don't think there's much "salt" to go around.