I have a thought, coming from Raspberry Pis that use a microSD card as their main disk. People would report that heavy usage of an SD card would wear it out, particularly writes. Does Steam or the OS do any writing to the disks while playing from them? If so, unless you’re downloading new games, mounting in read-only mode might extend their lives a bit. Again, just a thought and maybe it’s not an issue since it’s primarily reads being done, or maybe it’s crossed your mind already.
I work in a store that sells computer parts and we do pretty many sd card warranty replacements where the customer states that it was used in a steam deck and died in less than a year of use. So in my view the cards dying is true.
I'm not well versed in how steam handles things like saves, configs, etc. I would think if those are saved in the steam apps folder, then they are indeed written on the location the game is saves. RO would also prevent updates as well.
Overall I think the writing to disk is much less of a concern than say having a whole OS on there.
Does RPi's Raspbian support any boot moad like "toram?". I have no idea what size those OSes are for a pi, but I wonder if things like that would help too. I know some OSes are designed to be less write-intensive to prevent some of this as well.
Depends on the game, but there's going to be written sectors no matter what I would think. From Save games to generating terrain in things like Minecraft. It would be interesting if they could do a paired folder thing where all the writing would be done to the OS drive and read from the SD.
That being said, I think the wear will be much less than on the RPi since it's not running the actual OS off of it, not that I have anything to back up that theory...