Miners care a lot about ROI. FPGA seems too over priced, 4-6K per unit.
Mining with FPGA=Snakeoil?
At the current rate my ROI for my rig is 3 years.
A FPGA even with the current available not profitable bistream is 1 year but indeed, the warranty period is ridiculous.
While the warranty periods are pretty short, the longevity of FPGAs run within specs are not short at all. If the FPGA is run within spec then it is rated to run for 10 years of continuous operation. Failure of other components on the board is much more likely than a failing FPGA.