I am strongly in favour of listing the month of each trip with a provisional date setup.
The flexibility one is a sound argument, considering no matter what the date is, there will be several members wanting to go but cannot due to other commitments. I am all for the provisional dates from the start of each year as it enables people able to get time off work and work around other things happening in their schedules.
Perhaps a compromise system would work, where the more further distance meets involving accommodation and flights/long travel are given more permanent dates and notice, whilst the more local meets can be more flexible and may not need as much notice.