'Some day' could be years or even decades, If youre honestly worried then i would probably recommend building your own NAS - M-ATX mobo, weakest CPU you can find for that board, throw in 4gig of ram and use something like FREENAS or NAS4FREE for OS - that way its something does break it would be easily to find parts to replace it. throw it all in a shoebox or spend money on a small case like a NODE 304
A low powered AMD APU is highly recommended for a BYO NAS setup.
It would be more powerful then any pre-made NAS on the market, it would be louder and most likely eat more juice from mains but you get that 'fail safe' as parts can be replaced.
Otherwise depending what part of the world you are from its 2years warranty from Synology or Qnap - take the hard drives out RMA it, put it in the NAS thats sent back and everything should still be more or less the same as you left it.