I wanted to do this so bad back in like 2009. I archived MSN messenger chats and my texts and everything and I figured sometime in the future I'd be able to analyze them and maybe even train a chat bot to imitate me. But over the years I lost hard drives and cell phones and accidentally deleted stuff and yeah it didn't happen. Very cool this guy was able to do it
I used to have saving turned on for my MSN Messenger chats back around 2001-2004. I didn't lose them. 10-15 years later or so I had a look through them and the cringe was so powerful that I deleted them all anyway.
I mostly text on Signal with disappearing messages so I wouldn't be able to do this. Most people are fine with disappearing messages at 4 weeks, but a few people like to keep their chats forever.
I also use the Note to Self which is built into Signal and appears just like any other conversation. I use that for temporary stuff like addresses and keep it clean.
there's a tool for extracting chat history from signal desktop, you could build a plaintext and attachment archive with that if it runs regularly on your pc and appends new chats from the last run.