The current incentives for 150 points at Riviera are pretty good - as I recall, they actually got better from the prior incentive period which is very unusual. I’d say it’s a pretty good time to pick up 150 points there, especially if you have a September or October UY because you can use magical beginnings on the 2024 UY points for an effective $3,000 off.
Of course, I’d only buy RIV if you’re planning to keep for the long haul because the “drive off the lot” depreciation is pretty steep. Wasn’t a tough sell for me! I have 600 direct points there

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Current Poly incentives aren’t anything special, but hard to see them offering much in the way of better incentives given how sales are going there. Because Poly points are not subject to same resale restrictions as RIV, you don’t lose as much if you later decide to sell. If you don’t have a September or October UY, I’d say there isn’t a big risk of waiting - the price probably won’t come down, but that will be partially offset by paying less dues.
I believe today is the last day for AKL incentives so I’d make a pretty quick decision on that one. I’m not as familiar with that deal as it isn’t a resort for which I have wanted to own points (great place to stay, just don’t need home resort priority there as much since it is so big).