Just a few thoughts for you:

I've noticed some people telling you that 20 years (or even 15) is too
much, and quoting a bunch of stuff and scary examples. Speaking as
someone who has 600+ parachute jumps, including 8 emergency activations
(three of them on emergency parachutes greater than 20 years old and
two more on emergency parachutes more than 15 years old) and multiple
intentional single-parachute jumps (several on a parachute greater than
20 years old) and put put well over 100 first jump students (most of
them on reserves over 20 years old) I can only say that this is the
worst load of FUD (Fear, Uncertainty, Doubt) that I've seen on this
newsgroup in a while.

There is no life limit on parachutes on the US. Period, end of story,
not a gray area, not debatable. As long as the parachute passes
inspection, it is legal and safe to use. Life limits are used in
aviation when there is no effective non-destructive way to inspect a
component to assure it still meets standards. There are NO parts of a
parachute that can't be effectively inspected when it is being
repacked, thus there is no reason whatsoever for life limits. It's
really that simple.

People who understand and routinely use and pack parachutes (skydivers)
also understand this, and have no qualms about the age of a reserve (or
main) parachute that has been inspected. They also understand that the
number of times the parachute is packed and/or jumped does cause wear.
This wear is visible and inspectable.

The factory has an interest in limiting liability and making older
product go away. A dealer has an interest in selling new product.
Therefore, impartial opinions are not to be had from either.

The acid mesh problem is an ancient bugaboo. Once upon a time it was a
real issue. An AD was issued (AD's are issued on parachutes just like
they are on aircraft), some parachutes were tested, and the problem
went away. Manufacturers now have improved QC procedures so it is no
longer an issue.

Round personnel parachutes are old technology. There has been no
substantial improvement in that technology in decades. What's
manufactured today is barely distinguishable from what was manufactured
in 1980, changes to TSO notwithstanding.

Here is my advice to you:

Stay away from riggers who don't routinely jump - they are bad news.
Ideally, find a rigger who BASE jumps - they understand what's really
important when making a single canopy jump.

Go to your local drop zone. Not some fancy commercial operation with
turbine aircraft and tandems, but something more local and down home.
Talk to the jumpers who jump old gear, and find out who their rigger
is. Have him inspect and repack the parachute. If he considers it
sound, sell it - and give his name to the buyer.

Michael