Well am I lucky or am I good?
I got my first REV G. TIU in 03 and I didn't just plop it on the layout right away. I did some studying on the internals and critical thinking about how my KW transformer could kill this thing. Long before MTH issued a news flash about placing a fast blow fuse between the TIU and Transformer I decided to put a 7 Amp circuit breaker between my KW and TIU from the get go. This old TIU has seen many shorts and derailments and while it is not on the main layout anymore it still sees regular use on one of the portable layouts. The PSX-AC replaced the 7 amp circuit breaker for better protection as soon as I heard about it.
I'll fault MTH for lack documentation due to not putting the early model through some real world situations. But with proper Circuit & TVS protection, that TIU should last a very long time.