If it's portable (removeable) storage, and you back everything up (to a PC and a cloud account is best, at least for important files), if the card goes, you can always restore the files to a new card. (Most good manufacturers warranty the cards for longer than you'll want to keep them. [SanDisk's warranties are 5 years minimum, Ultra Plus and Extreme cards carry lifetime warranties.]) If it's adaptable (internal) storage and the card goes, there's nothing you can do - you can't back up an adoptable storage card.
But if the phone has limited storage (I'd call 16GB limited these days), you might have to put in an adoptable storage card to make the phone usable for a little longer.