I am hoping to breastfeed my next child during the day and for my DH to take over at nights. I have previously exclusively breastfed day and night but last time round I got so ill from repeated mastitis and sleep deprivation. My DH wanted this baby so badly and he needs very little sleep so before I even got pregnant he promised to do the night feeds to allow me some rest and to ensure that the baby takes a bottle and we can move to formula quickly if the recurrent mastitis is a problem again.
My plan is simply to breastfeed exclusively for a week so that my milk comes in etc and then to hand the baby to DH and the spare room at 11pm and to let him get on with it until 6/7am. We have bought some Avent bottles and a tub of Aptimal (we have never owned a bottle or formula before so this is all new). Do we need to think of anything else?
We mix feed and dd is 21 weeks. We introduced a bottle in the evening when she was about 6 weeks, and haven't looked back.
It started because she cluster fed for hours every night and I a) didn't feel like I had enough milk to settle her to sleep of an evening, and b) needed a break - just some time to myself. So we organised it that when it was her bedtime, DH would take her up with a bottle of formula to give me a rest (or have a bath or walk around aimlessly touching things with BOTH OF MY HANDS!).
Now she's a bit older and sleeping more we've changed it so that I put her to bed with a bf at around 7.30 (she's not cluster feeding any more!), and we dreamfeed her with a bottle at about midnight. This keeps her going until about 5am usually, at which point I bf her. I am leaking by that point though, my boobs are NOT clever enough to adjust to the longer overnight gap.
If I feel like I need more sleep one night, I'll go to bed at about 8 or 9, and with the dreamfeed that DH does it will give me an actual full night sleep - albeit between 8-5!
I also have more flexibility in going out because I know she can take a bottle.
It can work - I think whatever happens you're likely to end up feeling broken with tiredness at the beginning but just the introduction of one bottle really did help.
We mixed fed from day 2 for the same reason as you - I can't handle not getting a chunk of sleep. I did 8pm to 2am then DP did 2am to 8am. He'd give one or two bottles of formula during that time. It was a complete lifesaver and had no effect on my supply. We bfed till 6 months with the odd bottle in the day if it was more convenient but mostly bfing. I would wake up with sore leaky boobs for the first couple of months but it was more than worth it for me - at the very start sometimes I took a couple of panadol before bed to sort that out. I found it really handy to be able to do both and DD always settled just as well for DP and for me.
The truth is you can't know for sure if your supply will be affected or if it'll give you mastitis, but you can just try it and see. Lots of us have managed it just fine. If you do get mastitis you can just get the meds and quit straight away with no guilt. Same if your supply seems to be dipping. You're absolutely right not to go through that sleep deprivation again. It's not worth it.
You can get pre-made instant bottles that are great for night times, or cartons - far better than faffing around with formula for the first few weeks at least. Do make sure you've had a dry run of making up formula beforehand if you're going to go with powder. You don't want to be reading the instructions and figuring out the steriliser the first night home!