In other words, if I had a chance to record, search and navigate through real life conversations, I would have done that too; it is way better to have records than to try to remember things.
However to avoid 1) having to manually delete things and 2) accumulating hundreds of megabytes of messages and 3) to not be swamped by months and years of "can you call?", "alright, see you later" and other ultimately meaningless stuff, I have conversations in Signal with my frequent interlocutors set to expire after a month.
To save things, I currently simply screenshot the relevant parts of the conversation or forward them to my "Notes to myself" thingy for later. It's a bit manual, but at least it's simple to remember: what I don't actively save disappears. Screenshots leave out audio messages and gifs (to a certain extend) but it is at least something. (And I just realised that with Signal it's actually possible to download individual audio messages and video so that a later reconstitution is possible if tedious.)
However, what would be great is to indeed have a way to backup messages including stickers, audio, videos etc. in a more high-fidelity way to relive important converations.
In fact, shedding that memory shed cognitive distraction I did not know I had.
If I want to connect to people I do it here and now. Talking to the past in my head is unhealthy.
As a counter to that, I lost a close friend to suicide. It was really good to be able to reflect back on the conversations we had and relive the lighter moments we shared together. I agree that dwelling on those things can be unhealthy, but they can also be a valuable part of the healing process.
I went through the same in my 20s, grieved and moved on.
For what ever reason, reconnecting to it just makes me mad and depressed now. He’s not dealing with environmental collapse, political unrest, economic inequality, racism...
I find leaning into my anger over reality now leads me to be more productive than ennui over people no longer around to concern themselves with those issues.