With a family or 4 on just my income I don't have the resources to have a bag that just sits unused, I have to justify my gear by giving it as much use as possible.
My BOB/GHB/whatever you want to call it is a cabelback that I take on bike rides, short hikes, over night trips, etc.
First reason is I use some of the gear, the GPS logs our trips for example.
Consumabled would be food/water/batteries. I make up sort of my own MRE's, just take a zipock bag and put in a sncak or meal for each of us, breakfast bars or cliff bars, furit and nuts, etc. I'll have a few of those in My BOB and a few more made up at home. So when we are going to go on a longer bike ride and could use some of my bob food, I'll take an extra pack or two in my truck to refill as soon as we get done. Same with batteries and water, I take duplicates and those stay on the truck.
I rotate the food through my bob by buying new, putting it in the ziplocs and dating it then taking an older on to work to eat. This way my consumables don't expire as they are always rotating and carrying extra to the park or trailhead lets me use whats in the bob without fear or not having it.
As I get the funds I'm starting on bobs for each family member, going to get a camelak for my wife then add a few duplicates of consumables for her to carry too, then as the kids get older do the same for them.