Hopefully my R5 will last until the R5iii comes out... it still has 1 year of warranty left of the Canon Australia 5 year warranty period.
Even if it fails, I will get another R5 second hand to fit my underwater housing as I imagine the R5ii won't align with the controls. It will be expensive change when a new body and associated housing are bought together. Current R5 housing is USD1700 for my Ikelite system but "Pros" use Nauticam which are USD4800 just for the housing. The other bits can be reused though.
My L glass should last a lot longer although migrating from EF to RF lenses has been a pleasant (if expensive) experience. I am sure that the buyers of my used EF lenses are still happy with them.