CMV - driven marker for stable expression

[Graham Atherton]

Does anyone know how effective CMV driven eukaryotic selection 
marker genes are for deriving stably expressing cell lines, for 
example in NIH3T3? I know CMV gives high level expression in 
transient assay but does this level of expression rapidly die off
after say 7 - 10 days? - Thus would be no good if it were driving
a G418-resistance gene in cells under G418 selection for 14 days.
Cheers
Graham