Hi,
In effect IB awards are indefinite, it's just that the DWP checks your continuing eligibility at periods which usually match the period suggested by the health professional who examined you, if you had a medical.
So, if the health professional said that you should be re-referred in 12 months then that is when you are likely to receive your next IB50 questionnaire, regardless of whether or not you got your award due to an appeal.
The period allowed for returning a questionnaire is set out in the IB guides in the members area and there hasn't been any change to that.
Good luck,
Steve
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