Personally I've never understood the need some have for keeping chat histories. So this isn't a feature I'll use, but am sure others will.

And remember, Signal is a nonprofit. If you use it, and if you can, you should be donating.

I just had a use case the other day: my mom sent me a photo of a handwritten recipe from my great grandmother a year ago. I only remembered asking about asking, not about the response, so I was happy to still have that pic in my history. Had I downloaded the Pic, it would be lost among all the other crap I store all ocer the place. This way it was preserved with the context and even a voice message from my grandmother (not great grandmother) remarking on it.

It's my "old shoebox" with cherished memories of friends and relatives, some who have passed away.

Same.

Just save the pictures in the camera roll and important messages in your notes app of choice.