I have a backhoe and have run dozers but never an excavator so I have no experience for comparison. I'm looking at a Hitachi 160. I know the swing is central to it's operation but I don't know how much play or movement if any is "normal". Is it supposed to be as tight as the wheel on a truck that can spin both ways but isn't supposed to have any movement in the bearing? To test for movement, I swung the machine and stopped abruptly and could feel some play. The swing operation itself was smooth in both directions. Would it be more apparent if I dug with it? How can I test it? It has 6000 hours.
Typical up and down free movement in a slewing bearing is around 0.35 inch measured with a dial indicator mounted on the carbody and the gauge reading the bottom of the outside ring of the bearing. You can have free play in the pinion to ring gears also. That usually isn't a problem.
Be sure to also make sure the bolts that attach the house to the main baseplate directly above the slewing bearing are all tight. We had one the bolts all worked loose, this will also make you think that there is excessive play as you describe. We tightened all the bolts back and that took care of the problem for us. Good luck.