I try to keep multiple copies of digital pictures and occasionally I use a Fujifilm Instax camera to take instant photos (which should last a few decades if tre

I try to keep multiple copies of digital pictures and occasionally I use a Fujifilm Instax camera to take instant photos (which should last a few decades if treated properly - but it's a bit of a gamble, since noone I know has convincing arguments to support that claim). For exceptionally good photos, I'm considering prints on aluminum. These should last 50 years or longer with a little less care than Polaroids/Instax (i.e. they can be exposed to light).