Doing a little internet research, I found the following:

"The formal determination of "Time / Life" or service life of a non-military personnel parachute is still open ended and non specific. Someone must take the initiative and make a judgment
call to ground it. By comparison: "Personnel (military) parachutes have a determined service life (a maximum shelf life) without use of 16.5 years, and every personnel parachute is stamped with a manufacturing date that starts its life-cycle clock. A personnel parachute is also stamped with the date that it is first placed in service (PIS). From that point on, a parachute's service life cannot exceed 12 years. The longer the unit sits on the shelf the less service life it has once placed in service."
The Parachute Industry Association (PIA) has visited this issue without conclusion to date. Until the PIA specifies or recommends otherwise, it is the opinion of the current management at National Parachute that the maximum service life is 20 years from date of manufacture.
Emergency Parachute Manual P/N 81101-2P (Revised Dec. 2008)- 14 -"

And,:

"1.4 SERVICE LIFE
Independent testing of aged nylon materials has proven that its strength degrades over time, therefore, Para-Phernalia, Inc. and Free Flight Enterprises have established a 20-year service life from the date of component manufacture for the Softie Pilot Emergency System and the Preserve line of emergency parachutes.
1.5 Rigger Qualifications
In order to pack and maintain this parachute system, the FAA Senior or Master Rigger - or foreign equivalent - must possess an appropriate rating endorsement to their certificate. All SOFTIE models require a Back rating except the Seat model which requires a Seat rating endorsement. Because the Back models are also certified compatible with ramair parachutes when assembled with the Para-Phernalia ramair parachute deployment bag, the Rigger should be appropriately trained in the assembly and packing of these canopies prior to certifying the Softie for emergency use.
FAR 65.129 - No certificated parachute rigger may -
(e) Pack, maintain, or alter a parachute in any manner that deviates from the procedures approved by an FAA administrator OR the
manufacturer of the parachute; or
(f) Exercise the privileges of his certificate and type rating unless he understands the current manufacturer's instructions for the operation involved.
NOTE:
ANYONE who circumvents Para-Phernalia, Inc., assembly and packing instructions, or the packing instructions of the manufacturer of any of the component parts assembled with the Softie harness and container system, is in violation of FAR Part 65.129 and is therefore performing an illegal procedure.
10 Rev. 2.0 8/09"