Well, they kind of are. My brothers and I have been playing for about 6 years or so. (I started earlier, with first edition, and then stopped playing, we all took it back up with DMZ, and they played second edition, and then we re-started when I got back from Australia in 2001 with 3rd edition)
The guy who plays the psychotic street sam- he's been playing with us off and on since about 2002. He took a break for a couple of years to get his heart ripped out in Minnesota, and then he came back and started playing with us again.
Pretty much everyone else has only joined our group in the last few years- my fiance, her cousin, my other RPG friends... they're all more recent additions, and they're suffering from transferring directly from D&D to Shadowrun, which is a hard enough transformation by itself, much less EVERYONE in the group being new at it.
My biggest problem is that even though I have like 5 years of experience on most of these guys, they outnumber me, so when we are trying to plan, there's my plan, and four other REALLY BAD PLANS, and usually we end up going with one of the really bad plans.
Or, more recently, we go with one of my plans, and halfway through prep, someone gets bored and then wanders into danger and messes things up.
-kv