With only sixty pages (Editor’s update: 14,000 words) in which to present a thorough treatment of every issue, the Petitioner must balance depth of analysis against the number of challenges. The fear of estoppel often drives Petitioners to present many challenges with a shallow analysis that is supported by a perfunctory expert declaration rehashing the Petition. The Board often institutes on only a handful of such challenges, with the result that the Patent Owner can devote its sixty pages of Response to a much deeper analysis of many fewer issues. That deep analysis can expose gaps in the Petition evidence and trap the Petitioner in the “Death Valley” between the reasonable likelihood it demonstrated and the preponderance of evidence it seeks. (In PGR and CBM, the standard for institution is somewhat higher and requires a showing that at least one challenged claim more likely than not is unpatentable, if the Petitioner’s challenge were to go unrebutted.) Petitioners should take this potential mismatch into account when weighing the risk of estoppel over the risk of losing the IPR outright.