I meant it to be what @embray says - as close to two years as feasible, but *not* necessarily every 4 releases.  But if we have to pick "before" vs. "after" 2 years, I think we favor "after" - that is, we always guarantee an LTS for at least 2 years, but possibly 2 yr + a few months.

I'll clarify this in the document in a moment.