Our kids were on formula as well. Between kid 1 and 2 we did buy a Baby Brezza (aka the Formula Keurig) which I'm mentioning here solely because it was such an unexpectedly positive help. It cut the process of mixing+warming+testing the formula down to just hitting a button (and likely saved my sanity).
Warming? Testing? We gave our 3 cold bottles premade a few hours before right out of the fridge. Thankfully they never complained, and made our lives a hell of a lot easier. I weep for the parents who need to do the whole warming thing... seems like a giant PIA
