See my other comment. 20 years may be too long for some industries (software), but may not be long enough/ structured properly for R&D heavy industries like pharmaceuticals and biosciences.

Biologics (all the -mab drugs, monoclonal antibodies, adalimumab Humira) are a treat because you have to share your methodology, but you do not have to share your cell culture line. Since the cell line itself needs to be approved, the me-too's have to go through ALL the trouble themselves.

The problem is that there can be a significant amount of time between wanting to protect an idea and when you can effectively monetize that idea. It might take an inventor 10 years to work out the kinks in an invention and build a market for it to the point that they can really reap the rewards. I think anywhere between 10 and 20 years is a reasonable range.

On the other hand, copyright terms are just bat-shit insane and needs to be scaled back tremendously.