My mate brought a set of new Fournales for his Wideglide Harley, they recommend to send them back every year for service which was included in the price for new ones, one of the reason they cost so much new, but of course had to pay for postage and time it takes all, why so many don't send them back for servicing, he loved then as changed his WG handling and load carrying, they are an expensive shocks to buy new but back up service is great as well and a quick turn around.
Buying second hand and not knowing if they been sent back for servicing is a big unknown.