While running hot is clearly not conducive to a long life, neither is constantly plugging in /unplugging. Because all Switch Mode PSU's rectify the AC mains, and then apply it to a smoothing capacitor, there can be considerable surge currents at the moment they are connected to the supply. How big these currents are depends on the exact point in the AC cycle that "hits" those input stages, and is something the user has no control over. Even if you are lucky, and the moment of connection happens to coincide with the crossover point of the sine wave, the first couple of cycles still have to charge the capacitor up to working voltage. Blown diodes are a regular failure mode, or if you're really unlucky the capacitor itself might go
This also applies to those "Eco Friendly" Compact Fluorescent lamps that the EU are forcing on us. I once read a very in-depth article from an Australian blog, showing some which literally "blew up", and in a few cases actually caught fire.
The only way round this is to employ some sort of current limiting device between the mains and the PSU - this could be as crude as a variable resistor, or on more sophisticated equipment a "Zero Volt" switching circuit. But these all cost more, and the first case requires manual input. No guesses which applies to your "4p" Chinese made PSU!
I suppose you make a case for new homes to have dedicated circuits, purely to power all such chargers and PSU's, which could be fed by a (remotely controlled?) Zero Volt supply. This would greatly reduce the risk of a sudden failure and possible fire, but would anyone be prepared to pay?