FCOM 4.04.25 p7 states that the recommended parameters for changing winds in flight at consecutive waypoints are any variation of more than 30kts or 30 degrees.
Change the temperature if it varies by more than 5 degrees celcius.
In other words, all winds should be inserted before take off but only amended in flight if different by the above amounts.
Last edited by flyingins; 21st November 2009 at 08:17.