Long-standing is a term used to describe something that has been in existence for a long time. However, there are many other words and phrases that can be used to express the same meaning. Words such as established, enduring, persistent, and established are synonyms for long-standing. These words all imply a sense of longevity and stability, conveying the idea that something has been around for a significant amount of time. Other synonyms for long-standing include long-term, well-established, age-old, venerable, and entrenched. Using these synonyms can help to add variety and depth to your writing and make it more engaging for readers.