As far as 5 to 7, I think the math works out the same within the same category. If it doesn't I would get a 5 day cat 5 and use 2 days of cat 5 (1) day certificates to get to 7.

A Category 5 7 day package costs 35,000 more points than a 5 day package.

A Category 6 7 day package costs 50,000 more points than a 5 day package.

A Category 7 7 day package costs 60,000 more points than a 5 day package.

A Category 8 7 day package costs 60,000 more points than a 5 day package.

A Category 9 7 day package costs 45,000 more points than a 5 day package.

These numbers hold no matter how many air miles are in the package.

So, only for Category 7, is the cost of 5 +2 the same as the cost of a 7 night package.

However, if one is considering a Category 9 package, he gets a free night by booking the 7 night rather than the 5 night package. (Assuming he has 390000 points available.)

Art