I think it was last year with the Aussie Dollar's stellar performance against the USD, quite a few people were predicting parity with the USD but that did not happen.
In terms of "costs", viz. differences between now and the time you plan to be visiting due to the exchange rate fluctuations, one way is to buy what you need now and that way you have locked it the amount of US Dollar available to you and hence the cost certainty for your budgetary planning purposes.
