Windows Embedded products benefit from a long lifecycle. I covered this very topic in a previous post here.
You can find detailed information on when a specific Microsoft product (including Windows Embedded) will reach the end of its mainstream support or of its extended support on this website: www.microsoft.com/lifecycle.
For example for Windows CE 5 the mainstream support end date was 10/13/2009 while its extended support end date is 10/14/2014. Meaning customers who chose Windows CE 5 (available since 8/31/2004) can count on Microsoft’s support until 10/14/2014, not too bad, he?