All right, after a bit of research, I've concluded that the worst ending actually triggers not at the 10-hour mark, but the 37-hour mark. I pinpointed the exact amount by starting at two extremes and narrowing it down, using passwords from https://www.truepeacein.space/. This works on every OG cartridge I've tried, as well as emulators.

The reason the Justin Bailey code triggers it as well is because this password is not hard-coded with any special parameters. It has its own timer attached to it, which is actually set at 5090331 hours, well-past the 37-hour requirement!

I thought I'd post this question in the forum with the most accumulated knowledge of Metroid NES's inner workings. I apologize that it's not technically speedrun-related, but I haven't been able to find an answer anywhere else.

I recently acquired a first-edition, five-screw copy of Metroid, with the intention of getting all five endings. However, after leaving the game on and unpaused overnight for well over 10 hours, then completing it, Samus merely waves to the player in her full suit at the end. This is supposed to be for completing the game in 5-10 hours, whereas after 10 hours, she supposedly turns her back to you at the end in shame. I tried playing it again, this time without getting 100% of the items, but got the same 5-10 hour ending despite leaving the game running for nearly 24 hours. Can anyone explain why this happens?

Haha, thanks. I suppose there are places with folks better-fit to answer than this.

So, I'm an avid Zelda completionist. The games are a wonderful outlet for my OCD, along with collect-a-thons in general. I've put together a doc of steps for Ocarina of Time and Majora's Mask, for triggering every permanent flag (all cutscenes, owl appearances, one-time dialogues, room clears, etc, on top of all the regular 100% stuff), but the one thing that still eludes me is how Navi's dialogue flags work with the save format.

Is each hint she gives tied to a certain combination of bit-flips in the inf_table (https://wiki.cloudmodding.com/oot/Save_Format)? Or is her dialogue programmed around other flags, since her hints only change when you progress through the story? It seems like the latter would make more sense. The ultimate question I'm hoping can be answered by someone more knowledgeable of the save format's inner workings than I is whether or not I need to sit and wait for every one of Navi's unique hints in order to fully call the save file "perma-flag complete".

I have the same question about Tatl too, actually, especially since her hint flags appear to be tied to specific bits (https://tcrf.net/Proto:The_Legend_of_Zelda:_Majora%27s_Mask/Debug_Version/Event_Editor). I figured I'd mention that since they seem to be based on the same save format.