|Whoever told your that is wrong. However, it sounds like you are planning on storing the only copy of files on the external. All hard drives will eventually fail. Externals are more prone to fail for a number of reasons which I won't mention unless you really want to know. |
You should maintain at least two copies of any data you want to keep.
One option for you would be to get an enclosure with TWO hard drives inside that can save the data in RAID 1 mode which mirror each other.
Look at the link below. All the units listed should have 2 or more hard drives with flexibility on how to use them. The interface connections vary. The most common is USB. Your laptop is sure to have USB ports but may have additional, possibly faster connections.
Many of the units in the link are intended for network storage, which means you could use with two or more computers at once.