DC Comics is home to the longest running superhero books ever, but they often restart their titles. Golden Age comics had multiple characters in a single title, and the Silver Age gave heroes their own books. When a new character takes on the previous hero's identity, he or she gets a new series. The Flash, maybe more than any other character, has seen this the most.
Source:https://www.cbr.com/the-flash-best-first-issues/