[Fish Sandwich]

I definitely think it's gotten a bit out of hand in recent years, but I'm also in the camp that mostly doesn't sweat it too much if there are a few loose ends for a series I haven't seen. The actual main show with however many episodes, the big movies, and the random HBV type stuff are all pretty cleanly divided categories in my head.

Like, take Pretty Den-O – that's a perfect example of something you have absolutely no "need" to see unless you actively want that much Den-O. It's a situation where hardcore fans win and basically nobody loses, which is the ideal I think all spin-off content should be striving for. Stuff made during the series, rather than after, is where it tends to get messy, but even then, the main show usually provides ~just~ enough context to let the casual viewer stay a casual viewer if they want. Speaking from experience, not being able to watch Heisei Generations until half year a later didn't hurt too much when plot elements from it starting coming up in Ex-Aid, for example.