A hard drive wouldn't survive even 30 minutes in such a safe unfortunately. They're generally rated for paper and more recently for optical storage and NVRAM. The link claims 2 hours for flash storage products. Those temps would likely kill a hard drive though long before though.

I've had am empeg with 100GB and 30GB drives sitting in a safe for two years, which I just pulled out in the past three weeks. It's not doing so great, with a lot of issues reading, it will just stop playing a track at a random point. I haven't opened it up yet nor tried reformatting the disks.

My current media backup strategy is spare 1.5TB drives in their anti-static bags and off site. The data they're backing up sits on a dual-disk redundant 6 disk RAID 6 array. I've only just started this, but my plan is to make backups either monthly or bi-monthly.

Some of the data is replicated again on one or more additional drives that stay here at the house and get accessed once every few months.