SSDs mostly fail based on you using X amount of terabytes over the years.

Get a m.2 SSD, set it as your system install location and don't move games to and from the internal SSD often, let some games there to fill it and focus in the m.2.

Since I got a m.2 SSD and a external storage HDD to my PS5, I install the games directly to the m.2 and the ones I don't plan to play soon to the external HDD, moving between both of them, and letting the internal SSD with the games I play everyday like Genshin Impact and Zenless Zone Zero, which I haven't and won't move from it from years. Sure, those games update regularly but in the end it results in far, far less content being moved in the internal SSD.

It is a problem tho, yes it is. I do also believe people will eventually get around it to reliably replace the soldered SSD (if they can't already, really haven't troubled looking about it so soon), but I do hope Sony can allow the OS to be moved to the external SSD eventually, so that would make it a non-issue.

Don't really have high hopes for Sony to do anything consumer friendly right now, tho, but that is a problem for when the system is over 15 years old, and funny enough, with how shit is rough in the world regarding tech, I don't doubt the PS5 will still be very relevant and active when it's 15 years old, so it might be in their interest (as in making $) to actually care about it in a very long term.

I will enjoy my digital ps5 game collection on the ps7 in 20 years.

That may be the case however will the license still work

The only real solution here is to get 2 PS5s. Get another brand new ps5 and install all the games and updates for preservation purposes and then just use your current ps5 to play the games and do whatever you would normally do.