Quoted from DCFAN:Any light of any type used in any application is going to eventually fail, not just in pinball.
For WOZ it probably matters which type of boards are in the particular game to have an educated guess generally how long they will last.
In a recent WOZ thread, a buyer that bought WOZ and TH games with the new light boards had light board issues with both games. To your point, they are parts that could potentially fail (regardless if they are new or old board sets).