All things in moderation.*
Yes, porn can become an addiction.
How do you know when you an have a porn addiction?
The simple answer is, when it starts to rule your life.
When is that?
Generally, when you have a large collection of porn imagery and you are motivated to review it several times a day.
For most adolescents this is an expected phase in development that comes shortly after they discover the euphoric power that porn has on brain and body.
With sex and porn representing a 100-billion-dollar a year industry, it comes in second only to expenditures by the military-industrial complex, and is much safer for humanity.
"Moderation in all things," a statement about extremes being mankind's downfall, is said to date back to Plautus 2,500 years ago.