I have used Costco Travel for Cruises and Rental Cars, with largely positive outcomes.

Considering using it for an All-Inclusive, probably Mexico or Caribbean, just because of the cost.
Pacific Islands would be amazing, but Tahiti, Fiji, Cook Islands seem to all be significantly more $$$.

Just wondering if there were specific destinations you prefer, or specific resorts at those destinations?

Also, I am considering booking the flights altogether as a package. Any reasons for or against doing that?

I have always imagined it would be a 7-day trip. Are there any advantages to longer or shorter? I know with rental cars it seems like the Weekly Rate is a significant discount over a daily rate, but not sure if that applies here.

I appreciate your insights, O Ye Wise & Much Traveled Cougarboard.