Originally Posted by GogglesPisano

From the ALPA Guide: "Before beginning any reserve or FDP assignment, the flightcrew member must have received a 30
consecutive-hour rest within the past 168 consecutive
hours that precedes the beginning of the FDP."

The key: this is a look back rule. By the end of that last FDP you may be able to look back 168hrs and not see 30 consecutive hours rest -- and still be legal.