There are a variety of synonyms that can be used instead of the phrase "last forever." Examples include endure, persist, survive, remain, continue, and exist indefinitely. Other options include last eternally, go on perpetually, and hold up indefinitely. Each of these phrases conveys the idea that something will exist or continue for an extended period of time, perhaps even indefinitely. They can be used to describe the longevity of anything from a relationship to a piece of technology, from a cultural tradition to a physical structure. These phrases evoke a sense of permanence and timelessness, making them useful in a variety of contexts.