Lol storing a backup of a phone in a bank vault? Seriously?
unless you go to the bank every week then that backup seems a bit pointless to me. Am I missing something? Do people keep life critical things carried around with them on their mobile phone *and nowhere else*? (A backup of a full computer operating system is different, but the stuff stored on my phone at least is much more current...)
It may be funny to you, but I've heard that thieves love targeting iPhones, iPads, Macs etc. when they break into your home. Or it burns to the ground in a wildfire or blows away in a big windstorm.
I'd rather have a month-old archival backup offsite (bank, relative, friends or wherever) than none at all.
I'm suggesting hourly/daily backups on the drives close by and occasional, say monthly backups to your offsite location. My iPhone backups are NOT separate from my computer backups, since my iDevices sync with the Mac and then I TimeMachine + C.C.C. all the User data to 2 separate drives. One of these drives gets swapped once a month with the archival one.
If you want to go really fancy and have fast internet and high data caps, you could "near-line" your archival backups to a secondary or multiple locations.