In general, automated failover seems to make most small problems non-problems, but turns some small problems into big problems. It probably depends on actual numbers what makes sense for you app.

For some systems, I'd take getting rid of small outages -- I'll happily take an increased risk of a projected 15 minute loss of heart function becoming a >60 minute loss of heart function if it also eliminates what would otherwise be a bunch of 5 minute losses of heart function, since even the 5 minute interruptions would be fatal.

(Or, for a better example, revolvers vs. semi-autos. A revolver generally is more reliable, but if it goes out of timing, it's basically doomed, whereas a semi-auto can jam or pieces can break, but a monkey can clear, and a trained monkey can fix.)