An old argument

Sometimes one tries to stop a discussion saying that the argument of his opponent is old and known.
“Well, well it is an argument from granny’s wardrobe. It smells of mothballs. Don't you have something new?”.
In this case, the disputant is trying to discredit the argument as out of fashion.
But is it a fair objection?
Of course not! Arguments have no end date.
Until someone proves that an argument is invalid, it keeps its strength.
One needs to attack an argument, not its age. There are very good arguments since the days of ancient Greece.