Using memory as file cache is fine and to be expected/wanted. Paging out things that have not been used for a ‘long’ time is fine (i would think this is data rather than executable but could be wrong) I think I’ve even changed a setting on my astroberry to make it keep things in memory more rather than swap them out.
The problem is more why is kstars dying, is it a problem with the code, some linux setting or a bug in some part of linux. It could just be coincidence and it’s not actually the memory/swap that’s run out in some way. Really there’s a need to look at some core dump or trace to see what was happening when it failed. Pete seems the only one with the patience to take thousands of photos and it sounds like it takes a while to do. Unfortunately I don’t know enough to be able to advise how to get that dump, ages since I’ve looked at such a thing..

I agree with all that. To your point, swapiness is probably still set to the default of 60 encouraging paging rather than retention.

Yep that’s the setting I rather randomly changed
I also use zram/zswap for swap and even used tmpfs for /tmp (though ran into problems due to temporary files building up when doing plate solving). This all on a 4gb PI. I don’t think I’ve run out of ram and only ever had minimal swap usage so kstars/ekos isn’t exactly eating all the memory. That said I’ve only gotten things all working recently so have only taken around a hundred images in a session.

I used to have more problems when I used to take larger resolution images (with the same camera ) but stopped using the fits viewer all the time, switched off the notification sounds, changed to aps-c resolution and applied lots of updates which seems to have ‘cured’ that.No idea what it was though as it was quite random