Congratulations on your triplets!
I went to a lactation support workshop put on by the Fortune 500 I was working for. At the end, they asked when everyone was due and I said I was 5 months pg and eyebrows all shot up. I said, "Twins," and the leader of the group sighed really loudly and said something like, "well, if you can do it at all, it will be next to impossible." I was miffed but not deterred at all. I just thought she was rude to think of me as incapable of doing what I want to do. I assumed my body would know it was pg with twins and would supply the right stuff.
As it turned out, my twins were not preemie but one was in the IICN for several weeks. I took EBM to her but they were giving her milk through a tube and told me she needed it since she wasn't drinking enough from my breast. :/ They also were worried about the dads in the room when I nursed ~ actually said they thought it was great I was nursing but the men in the room might be uncomfortable seeing my breast.

In a NURSERY? I was really unsupported (and blacked out tired) and long story short, my supply never increased enough for both babies. I am really sad to say that once I started "supplementing" out of fear of my babies not thriving, it went straight downhill. Eventually they were FF exclusively.
I tell you this because I hope you'll know it
might be even harder than you think (I hope not) and it's possible you'll not end up exclusively BFing despite your very best intentions. I fought guilt for years about it, and I hope you'll not beat yourself up if it isn't in the cards for you & your babes.