Hi foghat,
Thaks for sharing your experience at Halsteads. Different body types will usually map out differently because the shape of the body and the weight distribution is different.
In general no … ILD is often not measured in the same way between different materials and there are many other factors and specs of a foam material (such as compression modulus, point elasticity, and layer thickness) that create a perception of softness that are just as important as ILD. You can read more about ILD comparisons in post #6 here.
All materials will soften … just at different rates … so even with latex occasional rotating or even flipping layers can extend their useful life.
Phoenix