How long does plasma last?

Technology has come a long way. There are many
rumors out there from strange to bizarre. One of them
is that you have to "recharge" the gas tubes every so often in order to see a picture! Statements like these have been running around for quite some time.

There is a fact sheet that was put out by Fujitsu explaining the myths about Plasma Televisions.
Without going through 20 minutes of myth busting,
they have a 1/2 life of around 8-10 years. One of the myths however is the term "life". It's not like the
TV will just stop performing after 8/10 years. What happens is they will gradually diminish in brightness
over the course of time. Usually this will happen so slightly that it will not be truly noticeable unless you compare a "used" set with a "new" set side by side. Truth of the matter is this actually happens with older televisions from the past. Compare a new set with one that is say 10 years old. Which will have the better picture?