On average, I use an instant cold-pack five times a month. I have an 8 year old boy, and he has a bunch of 8 year old friends. Put them together and you have plenty of ice-packs used. I keep a bunch in my Jeep too, for the usual sprains and bumps of life.
I carry a tiny cooler in the jeep as well, on occasion I pick something up that I'd like to keep cool and I don't have any ice, so I pop a large pack and throw it in there and it helps.
I keep a small one in my FAK, this gets used often enough. That leads to the inevitable FAK discussion, I'll just leave it at my kids are limited to mostly ways to stop the bleeding, sooth the bruise and burn, and that's about it. I have a very minimal pharmacy (Tylenol, immodium) and minimal tools (Medic Shears, BP Cuff and Stethoscope, Flashlight, Sam SPlint, Tweezers & Forceps). It's mostly about keeping things from getting worse, not making things better.