<< Yes, his songs were given time to stand through the test of times. You still hear songs by Beatles for example. But you don't reqlly hear any Eminem songs, even though it was only... what, a year since he was a "big star"? That means that his songs are not the ones that will be played years from now, since they are not played only year after their release. Sure, when he releases his new album, his new songs will get airtime. Only to be forgottten 12 months after their release. That didn't happen with Beatles, Led Zeppelin and the like. >>
Not totally. You have to look at the market and how it is different now days over years ago. The market that Eminem was targeting (or rather, his label) were probably 12-28 year olds. Looking at this group, they buy a lot of records, quite frequently. Because of that, labels scramble to put new music out there and wear out what is in "current rotation." However, there are generally quite a few tracks that are "radio songs" on CDs, and the label can usually milk a disc dry by releasing a track every few months. Next thing you know, you have been hearing new songs from Britney Spears for an entire year. I think Eminem's case is slightly different because there aren't that many radio songs (at least not without some serious editing). So, he's limited to having 1 or 2 playable songs. After they have run their course and record sales start leveling off or dipping, there was nothing else to hype the album. And, since record companies would rather throw a new N Sync song on there to sell some more albums or singles than have Eminem's six month old song, you don't hear Eminem any more.
I'm not backing Eminem here...You could substitute lots of bands in that same scenerio.
Now, oldies that have been mentioned and are a slightly different story. You have a huge catalog of songs that are played on oldies stations and those are targeted at older groups than Eminem targets, say 28-60 age. These are people that don't buy as many records typically. So, ad revenue is much more important here. These stations are living more off ad money and promotions than the record labels. They aren't getting new material in every week that is looking for an add. But, record labels support these stations as well, just not as actively. This demographic is more likely to buy a disc of songs they really like and might not have heard in awhile. If they hear something on the radio and remember it fondly or really liked it back in the day, they will pick up the disc, so record labels aren't totally ignoring these folks.
So, I'd say Eminem is working on new material right now. You'll probably catch his songs every now and again on radio, but it's probably few and far between right now. There just isn't that product to push right now.