Why is this necessary?

[will]

Can't you just use a private variable on the component for your timers, and then use the lifecycle method, componentWillUnmount, to clear appropriate "timeouts" and "intervals"?

This mixin is uses more power than it needs to. This use case could be solved simply by using a documented & official lifecycle method.

[Sophie Alpert]

Yes. This makes it harder to forget. What you suggest certainly works and is the approach I usually use.