There are several synonyms for the phrase "all night long" that can be used to add variety to your writing. Some of these synonyms include "throughout the night," "the whole night," "the entire night," "all night," and "nonstop throughout the night." Additionally, if you want to convey a specific mood or feeling, you can use more descriptive phrases such as "until dawn," "until the wee hours," or "until sunrise." No matter what synonym you choose, be sure it accurately reflects the duration and timing you want to convey in your writing. So, next time you need to talk about an event or activity that happened for an extended period of time, consider using one of these synonyms for "all night long".