Lead time for "how long until we can start using it" is one that is hard for a lot of folks to really take into consideration. There are terms for this, "earned value" and such. I have rarely seen them used in such a way that the planning actually worked out, long term.
I often end up saying, "I can build this, and I will build this if product insists on it, but first let me suggest an alternative ordering of deliverables that starts with a simple implementation and moves towards this one." In almost every case, that simple implementation is still what's in production years later.