Believe Colligo says 6 years for the Dyneema
Dux though the rep I talked to said it would probably last much longer. Apparently the fibers exposed to the sun protect those in the interior
of the line. Nice thing about Dyneema rigging
is that once you buy all the fittings, it's relatively cheap
to buy just the line and splice when it's time to replace.
There's a catamaran
just down from my boat
that has Dyneema shrouds. Don't know how long it's been in service
but definitely more than 3 years and still looks new.