Archie (above) and the gang are still teens despite the fact in real time they would be on retirement funds.
A floating timeline is an excused in pieces of fiction such as comics to explain why they don't age as much as they should. In a FT, events are changed so they happen more recently. For example, in a FT, if a comics says "10 years ago", it actually means "10 prior to you reading this". So, this is how come characters in lets say the Peanuts for example stay young even through the strip ran for 50 years. However, despite the characters not changing, technology and tends may change.
Comic Book Examples
- In DC and Marvel Comics, while the characters do age, it's at a much slower rate. For example, in 20 years, Spider-Man only aged 4 or 5 years.
- A better example is Archie, where the characters never age and have been in high school since 1941.