This is the time in seconds of a "Good for Time" (GFT) TimeInForce.
Positive integer value which represents the time is seconds in which the new order remains active in the market before it is automatically cancelled (e.g. expired).
Bi-lateral agreements will dictate the maximum value of this field. It is assumed that most systems will impose a max limit of 86,400 seconds (i.e. 24 hours).
For Quotes: The period of time a quoted price is tradable (i.e. on-the-wire) before it becomes indicative (i.e. off-the-wire).