Upvote:4
There are two separate things here: when the hotels run promotions, and what dates and which hotels are eligible for the promotions.
When promotional campaigns run is, in my experience, nearly random. This is on purpose: if the timing of the campaign was predictable, people would wait until the campaign to book discounted travel, which would cause the hotels to earn less money! There are some exceptions that do run to a schedule, like IHG PointBreaks, but these are severely limited to a small set of hotels that changes every time, meaning you can never really rely on them for planned travel. Which brings me to the second point:
The selection of what hotels are available when, on the other hand, is not random at all. Promotional campaigns are designed to incentivise spontaneous travel and to capture market share from competitors for business travel, so they target places in the off-season where there's plenty of free rooms chasing business: some revenue is still better than no revenue. But if it's New Year's Eve in Sydney, spring break in Palm Beach etc, forget it, every hotel will be booked anyway so there will be no promotional rates to be had, no matter how long you wait.