They were only expected to be there for three months when their missions started in 2004.
Since there is no way to remove the Rovers - they would be expected to be there forever (or until we get to Mars and bring them back and put them in a museum ...).
On the other hand, a more accurate statement would have indicated that ...They were only expected to function for a few months before they failed. The designer/builder was tasked to build the Rovers to last at least 30 days!
Maybe its a nit - but writers of scientific articles should strive to be technically accurate!
Mike
You are way too good about giving useful feedback.
The writer is an moronic idiot (alternatively, a idiotic moron). He needs to be slapped across the face, like three or four times maybe.