first, welcome to SS.
2nd - you'll hear all kinds of answers, but it comes down to this: it's a crap-shoot. folks will preach on and on about how proper PMCS will give you years of reliable, trouble-free service. and i don't disagree with this conjecture.
however, this is an old motor with an even older design. even though it has likely been rebuilt within the last 25 years and likely has very little hours on it, there really are no garrauntees. there have been several members on here that have suffered catastrophic failures even after years of meticulous PM service.
i'm not trying to deflate your balloon, just don't kid yourself into thinking that 'it won't ever happen to me'. just realize that it is what it is and take refuge in the fact that if you ever do have a serious problem that a rebuilt or take-out motor is usually readily available and very affordable. because of this, rebuild is not usually a practical option.
stay on the PMs, and you should have little concern. besides, i have more concern over wheel bearings, transmission, and brake failures than the engine by itself. those seem to be the 4 major systems suspect of unpredictable failure.