Given the extreme mimetic learning in children, it is probably important if the child sees you stopping a process they guess/know you are enjoying. The confusion which leads from questioning the reinforcement can be a source of wisdom. If the child sees you, the parent, put down the device after a few minutes, not gorging on food, sleep, and so on, having self moderation, they are more probably to also develop it.
The question then becomes how do you develop self moderation, which has been a question for at least the last 2,400 years with the socratic "how to achieve a good life" (by having an inner life) and the various "religions of the book" which are a proxy to this question, sprinkling in with a forklift supernatural beliefs (the good life is the one devoted to the God superclass, which has private, unknown methods to solve the confusion of reinforcement).
Coming to think of it, it is probably important if the child does not see you as a God superclass: they will try to rely on themselves (although it is a hard game to balance, not to be too traumatic), and they will be less inclined to rebel against you, achieving both their own personhood, but also being set up to follow your example.