Earlier quoted context omitted.
Exactly. I give services like this - generally coded as someone's first "wow I know PHP now!" or the modern equivalent - approximately 5 years shelf life, at best . Whereas I have notes-to-future-me on my calendar that I put there 30 years ago .
What calendar system have you been using for 30 years, that's survived that long? I think I sent one of those "mails to the future" in the 90's, asking 2002 me how I am. I don't think it ever arrived, or the free email domain I was using ceased operating. Sheesh, anyone old enough to remember the services offering a free email address with a choice of maybe 50 domains in a dropdown?
For the same reason, I have every email I've ever sent or received, going back to my 1988 FIDOnet account.