I am sure they are. A posi unit should last 100+ years if it isnt abused,so why wouldnt a new one last. I have been racing my race car for the last 17 years with the same shocks in it,and I still say my daily driver has "new" shocks because I put them in my last car 20 years ago,never drove it more then 500 miles,then moved them into my current daily driver 3 years ago and put another 5000 miles on them. I have seen parts that have been sitting on the shelf in speed shops for 25 years still being sold for new current prices(having the price raised 10 times to meet current prices). Most of the slow selling performance stuff that is is kept in stock in local speed shops is the better part of a decade.
1973 Camaro hot rod owned since 1989 runs high 12's. Mild 408 small block,th350,3.08 gears,ice cold a/c pumpin system ect.
1973 Firebird owned since 1994 runs mid 10's on motor and mid 9's on a 250 shot. BBC 439 2 speed,4.88 12 bolt,3600# full street car.
2011 Camaro RS,Jewel Tint.
2003 Silverado HD2500 and Wife's 2004 Malibu Maxx. Keeping my Family ALL GM!!!