This is actually a fairly well studied area and surprisingly even a term as short as two years would likely be enough to ensure that a profit was returned on the investment. Most media including books, movies, music and video games earns the overwhelming share of its profits in the first 4 weeks after its release and sales decay quickly in the first year hitting single digit percentage by year end. At two years out you'd be approaching zero. The curves differ between the media types (movies and video games decay fastest, music decays slowest) but they are close enough to generalize. The only major complication for an extremely short copyright length would be media that experience a resurgence due to developing a cult following, going viral or some other form of mass interest later on.

Personally, I'd still prefer a term of 10 years since it is psychologically more appealing and allows for the rarer cases where a work becomes popular well after its release. It would also be a better fit for music so it would avoid the complication of having different rules for different media types.