Supplementing a bottle of formula at night

Hi all-my 3.5 month old baby has been largely breastfed (except jaundice supplementation early in and some time when I was eliminating cow milk due to allergy). He’s also been a challenging sleeper, waking often (4+ times a night most nights). I’ve been exhausted and it is really not sustainable as I go back to work. Yesterday for various reasons I had to supplement with formula right before bed and for the first time in his life he slept 4 hours straight. I felt SO GOOD with such a long chunk I am trying it again tonight. He woke every 2hrs after that, but who cares! 4 hrs! Does any one else do this? I don’t produce enough breastmilk to have lots of extra pumped each night so if an extra feed is what helps him sleep I think it’s a good thing for both of us? Just curious about other peoples similar experience.