Shirley, I don't know much about this either as I've never had a dog that required that their anal glands be expressed. Mine still "scoot" once in a while, but they always pass their Vet checks, and I made a point of asking about this due to RJM's situation.
RJM had trouble with one of her dogs and ultimately had to have the glands removed. It was serious though, as I think he was leaving marks, and was experiencing a great deal of discomfort. I really would refer to your Vet on this. If they are 9 and 11, and have NEVER needed it before, it begs the question why now?
Some Groomers do it by rote. I don't know if they all do and it is something I will ask about next time.
This is a matter on which I would consult the Vet.