Redundant Power Input Protection

[stoic]

A bit of a generic / fundamental question regarding protection redundancy within circuits. Am grateful for your thoughts!

For good product design, is it still valid to rely on the built-in protection and filtering of an external DC wall-pack? For a low-power device (5 V input), hooked up to a quality DC wall adapter with proprietary polarized connectors, is it necessary to ALSO build in redundant power input circuitry onto circuit itself, for dealing with gross transient and reverse polarity conditions?

My circuit is battery powered and only plugged in for short periods of time to charge an internal lithium-ion battery. There's power management that will switch to wall power and charge the battery at the same time. There's some sensitive analogs in there and I’ve incorporated ESD protection, overcurrent protection, and minor overvoltage protection (i.e., Tolerating few volts above nominal by means of Zener). But is it sufficient to assume large overvoltage conditions (transients, etc.) will be filtered by the quality wall pack? In this case, it might open a large can of worms having to deal with thermal considerations during handling of large transients due to the battery aspect.

Thanks very much in advance,
-S