> If that asset generates revenue for 120 years, then it’s slightly more valuable than an asset that generates revenue for 119 years

Movies for instance make most of their revenue in the 2 week following their release in theater. Beyond, peoole who wanted to see it had already seen it and the others don't care.

I'd argue it's similar for other art form, even for music. The gain at the very end of the copyright lifetime is extremely marginal and doesn't influence spending decision, which is mostly measured on a return basis of at most 10 years.