Men should be off an equal time as women, not as a "so be it" measure. It's crazy that we push so much of the parenting to a single parent, effectively isolating her socially and never giving her time to be an adult or speak with other adults. Yes there's breastfeeding, but the best part of formula/pumping is that the mother can go out and actually be a human being while the dad can take over the duties with the child for a full day, night, or weekend!

[edited to add: even if the mother takes up the majority of the childrearing (diapers, feeding, swaddling, talking, socializing, etc) the father should be taking up all of her previous chores, housework, social maintenance (e.g. familial obligations)!]