Anicca (when and how?)

The Buddha put high emphasize on Anicca and thus it shouldn't be dismissed. Now my question: When should one remind oneself of the transience of all phenomena? I doubt in every occassion. If I for example walk or do my daily chores, according to the Buddha I apply Sati on the sense that I remember to not to forget walking. So this then is a rather concentration excercise without pañña (wisdom), right?