There is a point in time at which an option loses its value - it is no longer possible to Exercise an option to realise its value. As part of managing a portfolio of options, the conditions at which an option expires should be known.
In the traditional financial sense options expire by a certain date. This can be true in the real world, but there are plenty of other reasons why we may expire an option. This is a window of opportunity.
Until the point of expiry:
As Future work is an option and User Stories Are Options, Not Futures - how can the prime properties of options, namely their window of opportunity (Options expire), their value (Options have value) be applied to ordering a backlog?
Options expire