As far as I know, any foreign vehicle has to change registration if they are in country for 6 months or more.So If you get stopped you can claim that you arrived in country less than 6 months ago, and you should be able to get through a casual stop, but you will not survive a back ground check. Also if your insurance from home finds out you've been abroad for such a long time, it is safe to say that they will withdraw their cover and responsability they have toward you.
As Jayf1 said, buy yourself some peace of mind, and do the right thing.