Congratulations! Twins are amazing (and exhausting!)
I breastfed my twins. They were delivered at 34 + 4 by planned section due to IUGR and were in SCBU for 2 weeks where they were fed with expressed colostrum and then milk through NG tubes.
It was really hard going in the early weeks. While they were in SCBU I came home overnight but borrowed a pump from the hospital and set an alarm to express in the middle of the night (I was told that there is a time window in the early hours when production is greatest - or something like that, it's a while back now!)
We weren't allowed home from hospital until the staff were happy that they were gaining weight being exclusively BF. I fed them separately on demand which meant that I was pretty much constantly feeding or changing babies in the early weeks. I also swapped them daily from one side to the other, but kept one breast per baby for the day if that makes sense.
At about 5 weeks I was completely exhausted and felt that I couldn't carry on, so DH would give each baby a top up of a couple of ounces of formula in the evening to give me a bit of a break and which meant I could keep going.
I'm a firm believer in fed is fed, regardless of whether it is breast or bottle. I enjoyed the one to one time with each baby though and as a bonus the baby weight fell off me (I went back to Weight watchers and got double the extra breastfeeding points because I was feeding twins which meant I pretty much got double the daily food points so could get plenty of chocolate in there!)
So - it can be done, but it was relentless in the early days and weeks.