There is a lot of nonsense talked about 'data sheets' and junction temperature....
125 deg. c is the 'absolute maximum', it is NOT a pointer that you can reliably run the device at this temp or anything near it, generally it is the 'tits up' temperature at which point the devices reliability goes out of the window,
Basically it boils down to this.....
For every 10 deg. c over 25 deg. c, the life expectancy is halved.
This sort of result from an FPGA , can indicate poorly designed logic, an error in the logic, OVERCLOCKING or an inadequately designed regulator.
One major point often overlooked is that as the DC/DC regulator heats up the voltage regulation drifts.. and 0v1 in the wrong direction can toast the FPGA.
If it is the DC/DC convertor , take a look at the inductors if they overheat things can go bad very quickly...
what sort of 'algorithm' would be designed to allow a bump in the CLK frequency, it's not a 'crypto-currency' is it?