Thank you! The first question you linked seems particularly fitting: sorry I hadn't found that one before, or I may have not asked my question (which is however not strictly a dupe)

I'm not saying that the belief is founded, as he was most likely oversimplifying, but a police officer once told me there was no way I could go back, through passport control, to grab a sandwich at a restaurant in the "domestic" area, because I had for all purposes already left the country and I couldn't just go back and forth through the border. He should have probably said that they couldn't (easily) void then re-register my passage through the checks, but instead he said I had passed a border. Episodes like this may contribute to the misunderstanding.

I'd suggest changing the answer to state the 2-months deadline, as expressed by the source – then add any extra experience that would make you suggest a shorter deadline. I have already accepted the answer because the link in your comment was what I was looking for.

Thanks, this is what my question asked specifically! Would you have a source for that?

Thanks Hilmar for your reply. Are you aware of any accompanying measure to EC 261, or any legal precedent, that set a time frame for an application? In order to write "legal sounding letters with due dates" I should have a vague idea of whether they have crossed this line.