I know what you mean, DS used to breastfeed for 45m-1 hr at a time. And yes, I felt a bit resentful at mums saying breast is best and yadayada when they had babies who seemed able to have a complete feed by the simple act of kissing the nipple; obviously, what did they knew about spending 8 hrs a day with a baby to your breast, or the incesant pain, or DS vomiting my blood?. He sucked so hard the pump was sweet and kind by comparison. I had a problem with milk supply for allowing a day of rest to ONE of my breasts, and a month of putting baby on the breast and expressing when he was not there didn't bring the supply up. I stopped when I realised I was growing resentful of my baby and then, finally, life began. So no judgement from my part.
Since then, I have learned many things I didn't know at the time, like that there are BF counselors, although I'm aware this may not be what is needed in this case. What I'm trying to say is, that if I could do things again, in a different way I would try harder to find a solution to the problem, speak to more people, a BF counselor, HV or doctor, etc. before stoping.
In DS's case, giving him formula didn't change the things (apart from the pain, of course), he needed to feed as often as before and would take the same time to have the same amount on a bottle. But the formula brought in a lot of problems I was not expecting when switching like severe eczema, a permanent bloated tummy and constipation state which included desperate crying for hours when he needed to go. I understand this would NOT necessarily happen to every formula feed baby, but in our case, it did, unfortunately there was nobody around to believe me the formula was causing these problems, so we were left to cope with the problems on our own. After years of mentioning about milk he was finally diagnosed with dairy allergy being 3 yrs old!
Hence my suggestion, but as I said, you are the one who knows the situation better. If you think you can not cope anymore, stop. I'm just trying to tell you about some of the disadvantages we faced. Although is starting to seem like a very loooooooong way to say "no, don't use formula for hungry babies yet"
Best of luck in whatever you decide.