Hi Supravista,
Latex in general is the most durable of all the foam materials (polyfoam, memory foam, latex foam) and foam softening (virtual impressions) or sagging (visible impressions) are less likely to happen or will happen over a longer period of time than with other types of foam materials and if a latex mattress is inside a suitable range in terms of comfort and support (and isn’t “on the edge” of being too soft) then it would be reasonable to expect that it will last for many years.
Pillows are mentioned in a number of replies about various “symptoms” people may experience on a mattress (such as post #45 here) and using a pillow under the knees (for back sleepers) or in between the knees (for side sleepers) or using a body pillow to support the upper leg for some side sleepers can certainly help maintain neutral spine and joint alignment for those who need it but I don’t have any specific articles or replies just about using pillows for positioning no.
Phoenix