A few hours per cable seems excessive.
It depend on the needs.
If you need to have a BER (bit error rate) estimation with a good confidence level, the time grows very fast if you have no errors on a fast interface.
If you want to be 95% sure that BER is less than 1 in 10^12 (the standard value for 10G Ethernet), you need to transmit:
10^12 × -ln(1-0.95) ~= 3 × 10^12 bit
On a 10 Gb/s interface that is just 5 minutes, but as soon as one needs better BER or CL, the time goes up, e.g. for 10^-14 BER, 99% CL we are up to more than 12 hours!