What causes a pfd to wear out over time?

The elements, sun, water, and age can cause a PFD to wear out over time.
In boating terms, PFD stands for the personal floating device. The durability of PFD will be affected by all of the things above because they influence the corrosion rate of the material. 

Delusion is defined as an erroneous belief that if fixed and firmly held despite clear contradictory evidence

is a belief that is clearly false and that indicates an abnormality in the affected person's content of thought. The false belief is not accounted for by the person's cultural or religious background or his or her level of intelligence.