From my practice there are simple measures to avoid failures.
Do not place these boards in the closed case, setup the fan to cool the bottom layer of PCB.
Do not allow the local overheat of any component like DC/DC or external power connector.
Turn on the overtemperature shutdown in the bitstream, and control the temperature in the mining software. It is easy.
Then the FPGA board will work for years.
I am preparing a closed but see through box (plexiglass) with intake and outtake fans and HEPA filters for my babies

Electricity system will be separated from teh rest of my house utilities and with special protections and regulators. just in case. I will maybe add some Dire Straits music just for them to make sure they feels good.