I wouldn't want to give you advice because I don't know enough about these things. However, I'll just relate my experience with EAZ-Lift.
In the first year of towing, I added two bolts to the chains. There has to be some added flex with time and that's to be expected, and, at the end of my second season, I dropped the bolts and moved up a whole link. That was fine until a little way into the fourth year when things started to get a bit saggy again. Investigation revealed that the hitch receiver box was getting deformed and allowing just a fraction too much upwards movement of the hitch head. My dealer welded a small wedge on the shank to take up the slack a bit and everything seemed fine, although I'm still one chain link up on the original setting. I did notice that the washers on the U-shaped hasps at the end of the bars were also getting a bit deformed with wear and that would certainly account for some of the slack that needed to be dealt with by tightening up the chains.
Over the winter I'm going to get some professional advice about where to go next. A whole new EAZ-lift kit is inexpensive but I want to see what the guys with the experience have to say. I am going to get a new (and modified) hitch receiver for next year, though, as the present one is showing its frailties and suffering with our Canadian winters.