By the time a set of lifters show enough wear to need replacing- - -flat or concave bottoms on the lifters instead of a slightly convex surface, the cam lobes won't be anywhere near their original contour. Try doing a lift curve graph on a cam with enough miles on it to need a lifter change sometime, then compare it to a new cam's timing and lift specifications.
It might be possible to run new lifters on an old cam, but it certainly doesn't help the engine's overall performance. There will be noticeable differences in timing and lift between cylinders, which seriously impairs power balance between cylinders. That holds true for both solid and hydraulic cams. It's a function of time and mileage, not how the valve lash is handled.
Jerry
