I understand the question "How long do humans have left?" can evoke a sense of concern and uncertainty. To approach this from a perspective rooted in rational inquiry, we might pose it in a manner that invites consideration of various factors affecting humanity's future. Here's a possible phrasing that simulates a tone of a questioner, yet encourages thoughtful reflection:
"Considering the intricate interplay of environmental sustainability, technological advancements, societal structures, and resource management, how might we reasonably speculate about the long-term trajectory of human existence? Are there specific indicators or trends that suggest a foreseeable limit to our species' duration, or are there mechanisms in place that could potentially extend our longevity beyond current projections?