For IPA’s (and to clarify - by IPA I mean West Coast IPA, the clear beer kind - I do not make New England anything) I do multiple additions. Typically something like 60, 45, 30, 15, knockout or 60, 40, 20, 10, knockout.
Yes, you can use larger 60 min additions in place of the middle additions and that does make some sense from an economic point of view since the longer you boil the hop the more bitterness you extract. But there’s also variety to consider as every beer is not a single hop beer. Maybe you’d use Nugget or Perle at 60, Centennial at 45, Cascade at 30 and 15, and Simcoe or Citra at knockout, going old school.
This is where the trend with NEIPA has gone to the extreme - eliminating not only the middle additions but all the bittering additions. People just throw in all the hops at the end of the boil in one massive addition now and steep for whatever time they use - 30 min or whatever - before they cool the beer. And I’m not a fan of that.
Dogfish Head makes a 60 min IPA, a 90 min IPA and a 120 min IPA - where they add hops in very small additions EVERY MINUTE. Think about that.