The lifespan of any piece of equipment is determined by 2 factors;

The " Manufacturers Lifespan" & "Working Life"

The Manufacturers Lifespan as determined by the materials used is 10 years from the date of manufacturing.

The '' WORKING LIFE" of the TLA Magpie climbing harness is 5 years from the date of PURCHASE and depends on many factors, "Amount, Type, Conditions, etc" of its use and how it is cared for.
If your harness is cared for well, worn, replaceable items replaced and only given light use, it will obviously last longer than a product which is used heavily and not maintained.

This does not mean that a product will last for 10 years, from date of manufacturer and the product should be disposed of, regardless of your opinion of condition.

To deem a product safe to use, it should be regularly inspected by a qualified LOLER inspector. 

This inspection should be carried out at regular intervals as determined by the HSE every 6 months - and the harness should be removed from use immediately if any defects are found.