OK, there's two senses in which you can be put in the WRAG for a certain amount of time.
Firstly, when you're put in the WRAG, the decision maker notes when it would be appropriate to review your entitlement based on how soon the Atos practitioner thinks you will be fit for work. This amount of time is not set in stone.
Secondly, you will read about the time scale of a year for people in the WRAG in general, and this refers to new provisions in relation to the length of time which someone can receive contributions-based ESA, which is limited to a year. For a clear explanation of this by my colleague, see this link.
www.benefitsandwork.co.uk/forum?func=view&catid=10&id=83720