Given the number of software estimates that fail and the number of software projects that collapse, the vast majority of developers are incapable of doing so.

Given the number of software estimates that fail and the number of software projects that collapse, the vast majority of developers are incapable of doing so. If you are giving regularly accurate long-term estimates, I'd suggest that you create a consultancy that performs this service or teaches how to do it. Most companies and teams just aren't capable of doing this.