How do you know when to change your fly leader?

How do you know when to change your fly leader?

Three ways to attach a leader to a fly line

When Should I Change My Fly Leader? - The Fly Crate

Picking the Perfect Fly-Fishing Leader - Fly Fisherman

The Two Fly Setup The Fly Fishing Basics

When Should I Change My Fishing Line

CROWLEY LAKE FISHING ANYWAY YOU WANT!

Winter Fly Casting Practice - 3: Making Practice Leaders

Whipping a Loop in your Fly Line