Electromigration tends to get worse with small sizes but also higher voltage and temperatures. I could see a GPU wearing out that quickly if it were overclocked enough, but stock consumer GPUs will last much longer than that.
since electromigration is basically a matter of long, high-current interconnect, I guess I have been assuming it's merely designed around. By, for instance, having hundreds of power and ground pins, implying quite a robust on-chip distribution mesh, rather than a few high-current runs.
