The bottom line is that people should pay attention to the signals given to them by their body. If the earplugs make the noise sound like TV at normal volume, then it appears that it makes sense to stay. If the noise feels unpleasant even when one wears earplugs, then it makes sense (to me) to leave as soon as you can.
If I'm out and it's uncomfortably loud with earplugs in then I'm gone. I don't risk it anymore.
The reduction with a properly sealed ear canal is around 1000 times less powerful in terms of energy.