How long does your cycle last for ?

Slim • Been with my partner for 5 years now, been married for 3 years and working on baby #1
My cycle last for 4 days now. Is wasn't alway for 4 days it use to be 7 days then it went  for 7 days to 5 days. I'm 26 years old, I guess your cycle gets shorter as you age or something.