Vegas is the most difficult market to predict as it has more prices changes (and more extreme price changes) than any other market in the US. However, with this noted a few comments:
Really apples vs. oranges based upon the Valentine's Day Holiday. A similar example would be in NYC rates are generally low from mid-Dec thru February... but look for a room in Times Square on Dec 31st and it will be one of the most expensive nites of the year, no matter how cheap rates are for the same day a week earlier (12/24 or 1/7).
There is a third component that you didn't mention and it is the one that is often most overlooked by travelers of the mindset 'Rates will drop very close to arrival since hotels would rather get some revenue rather than no revenue if the room sits empty'. This third component is 'How much demand can we drive if we lower the price at the last minute' and the answer is very little. If hotels are priced at $200 and the day before arrival the hotel lowers the price to $100... there are not many people, who were not already planning on visiting the area, would suddenly pick up and take a trip on less than 24 hours notice? Even if they could potentially fill 50% more rooms by cutting the price in half, it actually produces less revenue for the hotel vs. if they kept prices at the higher amount. In case that is confusing, take the following example:
100 people plan on traveling but don't yet have hotel rooms: 100 guests x $200/nite = $20,000
100 people above + 50 additional people (50% increase in demand based upon lower price): 150 guests x $100/nite = $15,000
This also does not account for the fact that the hotel expected a certain level of occupancy and staffed their front desk, housekeeping, and restaurants accordingly... if there is a sudden surge in occupancy all of these areas of the hotel will be understaffed; leads to poor service, unhappy employees, and bad customer experience.
So with the reminder of my first comment that rates in Vegas change more frequently than any other market (and are therefore more difficult to predict), my inclination would be that low/mid-$100's is not likely going to happen for the 12/14 or 12/15. My gameplan would be one of the three options below:
Venetian at $223 (2/14-2/16) + Wynn at $146 (2/16)
1 Nite Outside of Vegas + 1 Nite wherever you can find 2/15 + 1 nite Wynn (2/16)
(OPTION 2 i think can wait, unless you wanted to lock in the nite at the Wynn, but my point is to understand that 3 hotels in 3 nites is going to be the most likely scenario)
Trump, which is slightly off strip, can be had for about $195/nite from 2/15-2/17
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Keep us updated on your progress.