You should't, there is no reason to risk it. You are always making more. Even though your chart says 10 hours, mine says 6-10. I am sure you know not to refreeze, but re-refridgerating is the same concept-it extends the time it has to break down. I am curious that you are only giving breast milk during the day. I have an almost 12 week old and I have learned that the formula does not necessarily make a baby sleep more, or longer. It really has to do with your baby's temperment. At night your body will make a fattier heavier milk for your baby. It may take a few more weeks for your milk to stabilize, but if you are skipping feedings you are going to produce less, and after you go back to work, really produce less. Night time feedings from the breast are sooooooo much easier, and as your baby gets bigger, you can feed while lying down in bed without having to go make bottles etc. This is how a mother naturally gets more rest at night. I went back to work at 6 weeks and my husband was convinced that in order for my son to sleep better, we should give him formula. I was pumping and feeding him formula, not getting any sleep, and he did not sleep one iota better. As soon as I began taking him into bed with me, and feeding him while laying down, I got so much more sleep it was amazing. this is a very natural process that has been going on with all animals since the beginning of time. Mom rests while baby eats. Your baby will wake during the day and sleep at night on his own time table. You cannot force them to change. If you keep going like you are, and go back to work, you will probably end up not breastfeeding because you will not produce enough milk. How can you when you are not feeding him during the day or night? Pumping does not stimulate milk production like the baby does. The health benefits are too good for your baby to give formula. It is very hard at first, very hard, but then it is so much easier, it almost makes the formula and bottles a joke. Make a commitment to yourself if you want to breastfeed and stick to it. I did, and although my baby just started sleeping well, not through the night but from 8 or 9 till 2 or 3 and then again until 6 or 7, I am glad I stuck to my guns. Also, what I used to help my son sleep at night was a swaddling blanket. Boppy brand, (online only item I think) or the miracle blanket now that he is bigger. I wrap him up, stick a nuk in his mouth, rock him a little, and he is out. Good luck, hope the advise helps!