I'm not sure how their corrected age affects things, but we only got it sorted about 2 weeks ago at 9 weeks. I made sure shed got the hang of bedtime 1st and just let her sleep so we didn't risk upsetting her BT pattern, then we introduced the DF (also works for me as I can only cope with changing 1 thing at a time!).
My LO actually seems to take more at the DF than any other feed. She's BF in the day so it's hard to tell, but recently I've been pumping off my right side as have a bad crack, and the most she's taken in the day has been 120ml. She'll take 150 for the DF and she will NOT let go til she's drunk every drop!
Congrats on your triplets, I am in awe!