For instance, those moving from stereo to surround work will need perhaps six outputs instead of two, while those who suddenly find themselves faced with a live band or other ensemble recording may suddenly require another half-dozen mic-input channels for multitrack work. There's been a recent spate of queries from musicians asking how feasible it is to add more inputs and outputs to an existing audio interface, as their recording and playback requirements become more sophisticated.
If you need more audio interfacing, do you really have to trash an interface that's otherwise perfectly satisfactory and buy a bigger one? Maybe not, as ways of using several smaller interfaces together are becoming easier to find.