Do bad things happen every time we don't remember state? is

remember{}

always recommended when dealing with some state?

That would depend on whether your use case requires the state to be recomputed for every recomposition or you want it to hold the state across the recompositions.

How often do recomposition happen?

Whenever compose feels like it, in terms of correctness. If you need a value to be the same across recompositions, remember it. 🙂

This is super useful - https://developer.android.com/jetpack/compose/mental-model#recomposition