No, a reasonable threshold is 10 years after creation.

The question is to what time threshold does society need to pay for police/courts/lawyers to enforce copyright law such that people are sufficiently incentivized to create whatever.

For example, if copyright law were 10 years from date of creation, would we see too little in the way of creativity? Would singers still sing and writers still write and artists still paint/draw/whatever?

I can see a viewpoint proposing 10, 15, even 20 years, but 100+ years is beyond the pale. That is just a handout from taxpayers to people that own the copyrights.