With a large account, you are more likely to have your posts to gain traction quickly. Frequency, however should still use a similar principle as with a smaller account. As soon as you see your engagement die down, make another post.
A lot of bigger brands post very frequently without even letting their previous posts die down. These accounts are usually brands and are much more likely to have all of their posts go viral, so they are much less concerned about posting too often. Brand exposure is what they are aiming for and their posts being consistently pushed to the masses, is a strategy that works for them.
If you were Selena Gomez (if you are reading this, chances are you are not), you can even post once a month and you would still get extremely high levels of engagement. But then again, she is the second biggest Instagram account after… you guessed it, @instagram.
As you can see, the best strategy, once again, depends on the goals, the audience and what your profile is about. There is no way to tell what will work better for you. You must test and then decide based on the data that you have gathered.
If you have chosen to go this route of posting a lot of content during the day, do not think that you will annoy your audience to the point of getting unfollowed. In instances like this, Instagram shadowbanning is your friend. Only a portion of people that follow you see your posts. Only a portion of people that look for the hashtags that you have in your posts, see your posts. So, no need to be worried that you will be showing up too much on everyone’s feed!