I just go off backblaze and gut feeling. Basically I have backblaze backup my data daily, if theres anything I really want to make sure is safe, I back that up elsewhere, and if its something I REALLY want to make sure is safe, I'll also put it on a local disk. If I ever got to the point where I REALLY REALLY want to make sure its safe, I'd probably try to keep a local version in someone elses house, but it hasn't come to that yet.

I know many here will say thats being negligent or whatever, I don't really care too much, I'd rather just get on with my life than jump through a load of hoops for data that I'm not too fussed about losing.