Now I think you have burst my security bubble with the flash drives... you did not mention portable hard drives though. I suppose all media has some kind of failure point... what about optical discs?
Maybe a routine renewal on any digital media is a good idea.
Any modern solid-state drive will be Flash memory. Hard-drives are pretty good, I've got some pretty old ones which still work OK (some have noisy bearings). Modern ultra-high density drives.... hmm, your guess is as good as mine as to how long they're likely to survive, powered off. All those itty bitty magnetic bits...?
Optical disks - the proper manufacturer pressed types are pretty good - some early CDs have been known to delaminate, but after the mid 1990s they got them about right. DVD & BluRay I've no idea. Writable optical disks are also subject to time-related failure; especially the re-writable ones. Basically the organic layer "goes off", you get read errors, it goes in the bin. Plus they scratch if you just look at them hard.
Regularly renewing your archives is definitely the way to do it. First, you get to know for sure that your data is sound. And you're constantly moving it onto newer technology which, whilst it may or may not be "better", is definitely less obsolete (how many of you still have 3.5" floppy disks, and use them? Ditto 5.25" disks? And since there's no reason to chuck out the old archive... you've got a bit more safety in numbers.
Paper is heavy and subject to rot and fire damage... nothing can be completely safe now can it?
True - it does require reasonable looking after - but keep the worst of the damp away, and/or fire obviously, then it's a lot more robust than anything digital... if you really must have the ultimate in security, then I can recommend a good stone carving company
If you don't want to go quite that far, acetate sheets - whilst not fireproof - are waterproof...