They will use them, and they sort of use them at the right time. I guess it depends on what kind of device you are talking about. They are kind of wasteful in my opinion when it comes to food and other healing objects.
The only things I do give my BOs are tribbles, so they can heal quicker between battles and save some medic skill time.
I used to give them hypos and food too, but they use those way too fast. I found that a tribble for every BO (except my Klingon ones, which they don't work for) and a Sci BO with decent heal powers is sufficient.