Yes, Wash!
I'll bet that your surveyor is the same soul I saw out in the pumpkin patch last week waiting for the appearance of the Great Pumpkin. There are no 'lubricants' in manufacured fibers. Plastics are composed of chemical compounds containing esthers that will migrate to the surface producing that oily feel. They can break down as a result of heat or UV exposure, but they can only be removed by chemical solvents.The real enemies of your lines are sun, heat and chafing. UV radiation breaks down the chemical composition of the fibres. Heat will destroy or weaken them and chafe is obvious. Dirt and salt are obviously abrasive and accelerate the internal breakdown caused by the heat generated from stretching. Mild bleach will not do substantial damage, but here is a case of 'less is more'. A washing machine is recommended because it takes a fair amount of agitation to get all the dirt and salt out of the internal fibres. Use of mild, low suds,low phosphate detergent is assumed. Fabric softener seems to reduce the stiffness and I am unaware of any damage concerns. Regular washing should be part of your maintenance routine.If the lines are as badly neglected as your description implies, replacement is in order not because washing is bad, but rather, because thier physical condition is highly suspect. In such a case, washing can be compared to painting over rust.Best Regards