Forever and a day and Long time

Forever and a day adverb - For a very long or seemingly endless time.

Long time and forever and a day are semantically related in very long time topic. In some cases you can use "Long time" instead a noun phrase "Forever and a day", when it comes to topics like long period of time.

Long time noun - A prolonged period of time.

Forever and a day and long time are semantically related in very long time topic. Sometimes you can use "Forever and a day" instead a noun phrase "Long time", if it concerns topics such as long period of time.