I don't have any experience at the Dunes, however I had a DID 520 ERT2 Chain on my XR 600 (628 kit)
for 5yrs with no trouble and very little stretch.
I figure it had about 40hrs. actual ride time on it when I sold the bike.
I do try to take care of my stuff, (maintenance!) and there was about 1-1/4" bow last time I took it off and cleaned soaked oiled it.
http://www.rockymountainatvmc.com/productDetail.do?navType=type&webTypeId=36&navTitle=Drive&webCatId=9&keyword=did+chains+er&prodFamilyId=973
Tuck\o/