(a) comes into force:
(i) on the day the notice is given under subsection 408(1), unless subparagraph (ii) applies; or
(ii) if a later day is specified in that notice--on that later day; and
(b) unless revoked earlier, remains in force:
(i) indefinitely, unless subparagraph (ii) applies; or
(ii) if that notice specifies the period for which the arrangement is to be in force--for that period.