Like most JS concepts, to me it's a "use it or lose it" situation. When I have to use them they are fresh in my head, when I move on to another project for 6 months that has no complex modules or uses a framework like Angular, there is no way I'll remember the intricacies. That being said, there is still a different between having used them and simply being aware of their existence, which I suppose could be made clear during an interview.