A lens hood is usually worth carrying, and many photographers simply leave it on most of the time.

Its main job is to block stray light that can cause flare and reduce contrast, especially when bright light is coming from the side or just outside the frame. It also gives some physical protection to the front of the lens if you bump it.

There isn’t a fixed number of shots or amount of time per day when it helps—it depends on the light and shooting angle. In practice, it can help often enough that many people treat it as the default setup.

Common times to keep it on:

• general outdoor shooting
• scenes with strong side light
• whenever you want maximum contrast and less flare
• for extra front-element protection

Times you might remove it:

• if it gets in the way physically
• very close-up work where the hood interferes
• if it could cast a shadow in strong directional light
• if you intentionally want flare for creative effect
• briefly when changing filters

So the simple answer: yes, it’s generally worth using regularly, and leaving it on by default is a sensible approach.