You can only book through late December or early January now, but this is what Etihad says about ticket validity:
3.2 PERIOD OF VALIDITY
3.2.1 Except as otherwise provided in the Ticket, in these Conditions, or in applicable Tariffs (which may limit the validity of a ticket, in which case the limitation will be shown on the Ticket), a Ticket is valid for:
3.2.1.1 One year from the date of issue, if completely unused; or
3.2.1.2 Subject to the first travel occurring within one year from the date of issue, one year from the date of first travel under the Ticket

So I interpret that to mean that once you travel the first segment, you can move the rest of the flights as late as one year from your initial date of travel. So if you book in Dec 2014 for the outbound CMB-DFW, you will be able to move flights as late as Dec 2015 after you fly the first segment.

Read the fare rules posted earlier in the thread, or look them up on ExpertFlyer or even ITA. They specify unlimited stopovers and transfers with no HIP check.