well longest iDevice would be atv3 has yet to be jailbroken.. but i dont really count that
umm ipod touch 2g was about 5 months, ipad 2 4 months.
The ip5 is for sure taking some time but by all means its still not as bad as people are making it out to be. Almost all jailbreaks pre ip4s the devs didnt really update like pod2g did.. So i think people just are expecting updates like last year..since they dont hear any they are flipping out.