The MTHS parameter has been added to the system which specifies the number of months ahead. So if it is currently April and MTHS is set to 13 then guests can book up to the end of April the next year.
The default is 13 is MTHS is not specified.
In the following screen shot example the current month is April 2014 and MTHS is set to 13.
Once March 2015 is displayed the hyperlink to April (ringed in green) is still available, but the links to May and June (ringed in red) are no longer active.