Both should be changed regularly, and both for the same reason.
Two!.......pac. (*It's a lot better spoken than written.*)
Thirty.
One of them is a big puss
logic
They both need to be changed after a while for the same reason
Ask Hugh Hefner.
Dads joke) The same reason 10 pennies is worth more than 9.
A: The same reason they sing Hymns instead of Hers!