Does this review hearing have to be made known at the time the rehabilitative alimony is determined?

It should be to eliminate surprises, but it may not be absolutely necessary. That is, if the agreement or order does not contain a provision for a review hearing, it may still be reviewed, depending upon the laws of your state.

If you want the rehabilitative alimony to be reviewed, you should include such a provision or clause stating so in your agreement.

Typically a spousal support or alimony order is not easily modified at a later date unless it is stated in the decree or judgment. If this were not the case, you would have a lot of ex-spouses tying up the courts. Child support on the other hand can always be modified, because it is the responsibility of the court to look out for and protect the best interests of the child(ren).