That shouldn't really happen, the cable should have a much longer service life. 

But we have had at least 4 instances where the heated bed power cord breaks easily due to metal fatigue from a lot of bending when the bed goes back and forth at fast speed thousands of times.

We have determined the real cause is that the cable is not properly attached and zipped tied to the bed.

1) The cable end with the spiral spring of the cable goes to the heated bed, not the PCB.

2) The two holes near the heated bed connector serves as the base for zip tying the cable firmly in place.

3) The cable should be zipped tied around the fat rubber insulation of the cable (not the 4 wires because we don't want the actual bending to happen there.)

Please check how your cable for the heated bed is attached and zipped tied. If it is not as described above, please change the arrangement accordingly. Doing so will give your heated bed cable a longer life.

This topic has been posted in Trinus Creatives group, with an easy to follow picture: