I have 70,000 miles on the HD arms and bushings. Very responsive, and still tight, both the ball joint and bushing. Now, the caveat: they do transmit more vibration and harshness to the steering column. Your wheels must be perfectly balance and the front rotors can not have much run out.
That said...the HD's out last the OEM's by a significant amount. I would guess 3 times plus. My original factory parts were shot after 50,000 miles and the bushing were crapping out at 30,000 miles.