Okay, but IP protections exist to benefit society. Being less harmful isn't good enough, the justification has to be "here's how being longer than twenty years benefits society".
Do movie companies or authors choose to make stuff because they'll be able to pick up more revenue 25 or 50 years from now? Seems unlikely. Both indiviudals and corporations are typically focused on the immediate future.
Snow White entering the public domain is not a particular benefit to society.
A book which is long out of print, with ambiguous copyright status is.
OP's idea was that copyright renewal costs would skyrocket after 30-ish years - I'd presume the intended benefits to the public would come from (1) increased revenue to the Treasury, and (2) most creative works leaving copyright in 30 or 35 years, because even GigaGreedyCo would only pay the renewal fees for a few of their most lucrative works.
30 years doesn't seem very objectionable to me. That's about what it was in the US in the 1800's. From an author's PoV - yes, there probably are niches where an optimist could figure "I'll write one each year. Sales of each will be low - but if I can work up to having 30 of 'em in copyright, then the total royalties will let me live comfortably." And your "immediate future" argument seems to contradict how many people plan their careers and save for retirement.
I also feel like protecting Disney is a net benefit, because they can chose what goes into public domain, based on cost.
Whereas that orphaned work you have never heard of could find a new audience.
I've considered artists lifetime or 20 years whichever is longer too.