That's a good question. All I can offer is the following: When Lionel offered the reproduction of the pre-war Hiawatha many people reported casting failure X number of years later (I don't remember the time of the exact postings). I have one of the sets and at that time I checked my set and found everything to be OK.
I've run the train from time to time in the years since 1988 and each time I've pulled the set out it looked fine. Recently I pulled it out for a running session (I hadn't run it in a couple of years) and it is obvious that the main casting for the engine is starting to fail as are two of the undercarriage castings for the cars. So, from 1988 to roughly 2015/16 nothing happened but then sometime in the last two years things started changing.
Given the history of the failure of the modern die castings I would say that all you can do is wait and see.
