Another useful rule: don't be a completist for its own sake. There are very few worthwhile sequels to horror films or to Hong Kong action movies. Even Kurosawa, Kubrick and Hitchcock had their off days. Season 3 of ST:TOS has almost no good episodes, and is not worth $90. The Phantom Menace has almost no good scenes and is not worth $2 and 2cm of shelf space. And so on.