as and when
When it becomes necessary to do something. We'll worry about that issue as and when it arises, all right?
as and when
used to refer to an uncertain future event. 1996 She The single most important strategy you can adopt to boost your energy levels is to learn to deal with an issue as and when it rears its head.
ˌas and ˈwhen
whenever; at the moment when: We’ll deal with individual problems as and when they arise.