In general, we agree, as well, however, with the caveat that not all frequent traveler credits are created equal. Some trips( those taken with OAT in particular ) offer very generous travel credits because of the cost of the trip. Given the fact, as has already been stated, that the 'last minute deals' are not as generous as previously, it is conceivable that one's frequent traveler credits can actually be as large as the perceived last minute discount. The Good Buy discount is another matter, and can be as large as 10%pp, if the trip is booked sufficiently in advance.
We also concur with nanaandpapa about planning our trips in advance so as to maximize savings. We 'saved' just about 25% on our upcoming trip to Nepal, Bhutan and Tibet by combining those credits and by pre-booking. And it is not likely that this trip with the extensions will be available on a 'last minute deal,' in consideration of OAT's small group size.
Of course, if one is exteemely flexible as to their personal schedules, and wants to take advantage of a serendipitously occurring trip availability, on a whim on short notice, the 'last minute deals' do offer savings.