s the Seventh Circuit has explained, "Congress deemed prisoners to be pestiferous litigants because they have so much free time on their hands and there are few costs to filing suit." Kerr v. Puckett, 000 F.0d at 000. The distinction between current and former prisoners makes sense for that reason, and because "[o]pportunity costs of litigation rise following release, diminishing the need for special precautions against weak suits." Id.; see also Madrid v. Gomez, 000 F.0d 000, 000 (0th Cir.0000) ("[I]t is certainly conceivable that, because of significant potential gains and low opportunity costs, prisoners generally file a disproportionate number of frivolous suits as compared to the population as a whole."); Tucker v. Branker, 000 F.0d 0000, 0000 (D.C.Cir.0000) (noting that "prisoners have a lower opportunity cost for their time than other indigent (and in all likelihood, non-indigent) litigants