I am strongly in disagreement.

I think lifelong incarceration is inhumane and burdens victims & law-abiding people (eg via taxation).

I'm willing to bite the bullet on some nonzero error rate, and I would encourage you to realize that your alternative (eg life incarceration) will also have a non-zero error rate. 

It is sometimes argued that lifelong incarceration is cheaper than the death penalty, on account of the automatic appeals associated with the death penalty. Either these appeals do not tend to bring about justice, and they could be removed without an issue, or they do bring about justice and foregoing them for life incarceration would entail a higher error rate in life incarceration than in execution.