Nowadays I am adopting the "Mom Strategy for Subscriptions (TM)": Eat what is in your plate before asking for more stuff.

I tried this idea for the books and gave up. No rules for book purchases.

But for something like netflix, I create a list. And when I start repeating something like Seinfeld, Breaking Bad, etc. rather than not-yet-watched items from the list, I cancel the subscription. And I don't renew till some time passes (6 months). Only then there are a few different movies/ series I can add to the list.