i say do what `bubbadreier` said, and have some small attachements that can be added to the bag. one bag can have your biological equipment, one can have your extra ammo for the zombies, another can have some type of climbing equipment for the earthquakes or if you live near some where that needs to climb.
but at the same time, what different scenarios are there to have multiple bags for? i have my main bug out bag, which can assist me for 72 hours or more. i have a get home bag in my truck that has enough items inside that will get me home within 12-24 hours. i have a small emergency road kit, which include jumber cables, smal tire pump, tire fix, some water, non perishable food, blanket, flare, and other roadside asstance stuff. my wife has her bug out bag. i have a small bag at work in a locker that i never use, which include some food and water and small items that if it get stolen i wont miss, kind of like a edc kit. i have another back up bag in my storage unit. they all have similar items, but are meant for an every scenario type of bag. i dont have full hazmat suits in them but at least hey all have some basic necessities that will help me (what i call) slow down the dying process.
like cpr for example: you may die in 3-7 minutes, but if some one is performing cpr on you, they are slowing down your dying time, and you may die withing 10-15 minutes, but those extra minutes is enough for the E.M.T.'s to come and give you the aed and some saline in you, and that o2 in your system.