Synonyms for the phrase "of all time" include "ever," "forever," "eternal," "perpetual," "timeless," "enduring," "everlasting," "ageless," "unending," "continual," "unfading," "immortal," "immutable," "persistent," "abiding," "uninterrupted," "indefinite," and "unceasing." These alternatives can be used in a variety of contexts to convey a sense of permanence or historical significance. For example, one might refer to a painting as a "timeless masterpiece" or a book as an "enduring classic." Whatever term is selected, it should evoke a sense of enduring relevance or significance - something that has stood the test of time and will continue to do so.