Sales Orders consuming inactive forecast sets

Hi -

We are seeing cases where sales orders are consuming inactive forecast sets.  For example, forecast set has been inactive since July 2013 and yet sales orders after July 2013 are still consuming the forecast set.  While this has no impact on planning, since the disabled forecast set is not used as demand, the client is not too happy with this result and any attempts to re-assure them are not working.  Is there any settings or configurations we can make to turn off this feature?

Thanks