It is hard to say what will happen to your milk supply - some mums can continue to feed just once or twice a day, but their supply will even out, so you probably won't get that fullness that by the sounds of you get at the moment, to keep that going you would have to keep expressing. Does that make sense? Based on the whole supply = demand thing.
Have you tried doing some breast massage, warm washers or nipple stimulation prior to a feed to help encourage a faster let-down and give bub the "reward" straight away?
Another suggestion I have for you is there are these comp feeder things (can't remember what exactly they are called, but there is info on the ABA website) where you put a tube in the bubs mouth at the same time as breastfeeding and drip EBM/formula into her mouth as she suckles at the breast so she is encouraged to continue and once you have a let-down you stop the bottle supply and allow her to keep breastfeeding as normal.
It is normal around this age for babies to start becoming impatient and curious with their surroundings, feeds can be a bit of a pain - all you want them to do is settle down and suckle but they are looking around, on/off the breast and then they look at you like - Mama, where is my milk... I want it now! Some people find success in wearing a necklace or playing with bubs hands etc to encourage them to focus on the task at hand and therefore let-down sooner and help baby have a nice feed.
Up to you what you decide, but if you do start giving formula you will notice a supply drop and if you are aiming for a once a day feed, it might be possible but be prepared that you may lose most of your supply