I have to admit, that is also 1 of my worries, but your graph doensst say that much without knowing what kind of stress is generated by typing / the occasional stress peak. So you have a source with more background info?
I know this board is build for flex, but tbh I dont care too much about that. I'm planning on building mine with a plate and loaded with foam, so thats going to relief a lot of stress from the 'flex fingers' on the PCB.
And just to be sure I added a spare PCB just in case.
That said there were/are a couple of weird things with the GB. The first thing is the shipment cost. The announcement said 60 USD worldwide, but when ordering extras this increases tremendously (110 usd shipping in my case). I hope the team will look into this.
Also the plate availability is odd. There is different info on various places on the site. It seems now there is no POM option. Not sure if this is an error in the GB listing or it will be offered at a later stage. Or not at all.