Personally I would not get caught up in wiring limit switches on a machine of this size, you are using steppers so they will stall if they come into a hard stop, If you were using servos or looking at 500-1000ipm rapids then they would probably be a good idea
I have to agree with this. I was planning on wiring limits on my mill just for the feeling of safety, but I never use the homing function on a mill and it just takes up travel. Glad I didn't bother because it really wouldn't be protecting anything on my machine.