It is so hard isn't it. The hardest thing I ever had to do. and, honestly, the best thing you can do is just give in to it - for a wee while. The hormones are all over the place and it is such an emotional time anyway. There will be time for strength and courage, but right now, have a weep, eat large amounts of chocolate, and feel a little sorry for yourself.
With each day, it gets - well, not easier - but less painful to leave. And the hope you feel as you see them grow and take their little baby steps in this world, will carry you through the process.
Nobody can tell you how long they will be there, but as has been said, there will be a routine of sorts and you come to appreciate the time you have to heal, and get better and stronger so when they do finally come home, you are ready to deal with whatever that brings. I look back on the 6 weeks Abby was in NNICU and it was full of joyful firsts - off the c-pap, first cuddles, first breastfeed, first time in the cot. There are so many more "moments" you get with premmie babies that most mothers never get to experience.
And at the end of that journey you will have learned so much about yourself and you realise just how special you and your babies are.
We've all got you in our thoughts and hope your little ones are home with you very soon. In the meantime we are all here for you, anytime you need to vent or rant or ask or even just share the happy news with us.