Time waits for no-one.
In an industry as relentless and brutally competitive as professional football, reaching the top level is hard enough, let alone staying there for 20 years.
More than just talent, it takes a special mindset - a remarkable amount of focus, dedication and drive, especially with the increased demands of the modern era. Few are up to the challenge.
Should James Milner make his 600th Premier League appearance against Tottenham on Sunday - and though he was taken off against Napoli on Tuesday, manager Jurgen Klopp said he "seems fine" - he will join an exclusive list.