A parachute life and even the repack periods are historical rather than a
period calculated to be safe, as the Stong article would seem to
indicate.
Originally parachutes were made from natural fibres, cotton for the
container and silk for the canopy. Both these materials do deteriorate
over time. The service life and repack periods appear to have been
arbitary time periods. Certainly the 6 month repack period goes back to
the days of silk canopies and was probably necessary.
With the increased use of synthetic fibres the life period certainly
became obsolete although some parachute manufacturers hung on to the old
limits, well they would wouldn't they if they wanted to sell the things.
It seems that the yardstick is now that if you can get a rigger to repack
it no problem.
The biggest problem appears to be that fitting a new canopy or container
may not be an option. For example the original EB80 used the I 24 canopy,
the latest versions uses the H 112 canopy. It appears that the I 24 is
still available so all may not be lost