To limit the number of months on the booking form from the property page you must do the following
In js/property.js file

Look for the function check_in_out_enable2 (should be around line 150) and add this piece of code  – replace 3 with your number of Months

var futureMonth = moment(today).add(3, 'M');


The above code will be one that limits the number of months.

After that  add

maxDate:futureMonth,

in the options object – should end up with something like

var options = {
opens:calendar_opens,
singleDatePicker: false,
autoApply: true,
alwaysShowCalendars: true,
autoUpdateInput: false,
minDate:today,
maxDate:futureMonth,
locale:{
daysOfWeek:dayNamesShort,
monthNames:longmonths
},
isCustomDate:wpestate_booking_show_booked,
};