Without getting into the primary versus secondary question (i.e., where the aging occurs), an IPA will benefit from bulk or bottle aging for a month or so after fermentation is complete before drinking, like any other pale ale.
+1
And an IPA will benefit just as much from any other style of beer from a month in some combination of all primary or primary + secondary, especially with dry hopping.
Basically the idea that and IPA needs to be consumend "young" really just means that if you stick your IPA in a bottle for a year and sample it, it won't be an IPA anymore....but it WILL be a nice pale ale....
At some point, whether it is 3 or 6 or how many months, hop quality will start to dissipate. But if you are bottle conditioning you are still going to need a minimum of 3 weeks, if not more for the beer to carb and condition.