as i see it is like the guys near my town, they think they are more "motocross rider" because they had the 2010 bike, the 2011's bike, now they have 2012 bike, and sure they'll get the next years bike. why so much trade?! some of those bikes fail time to time, or maybe it's just fashion to have the lastest year bike, with shinny new plastics even if they that the bike will be the same as in the last 5 years. if they would swap for a reliable bike, even if it's an older model?? hell no, why!? in theyr head "what people will say if i show up with an old bike..oh man, i gotta carry oil in my backpack if i ride a big trail session!"
it's true, i've seen it!! MXA is available here in Portugal, they get the magazine and i ear them talking about non sense bike improvments from a year to another and a bit latter they'll decide to trade theyr bikes.
local bike shops have loads of 4 stroke bikes, 2 or 3 new ones, and 10 of them from 05 to 2011 in mint condition, that's why i say it's fashion to trade bikes nowadays..