[hong]

What is the average lifespan of an average external hard disk drive?

Is SSD the way to go?

[Egregious]

Depends how you're using the drives. SSD spec sheets list a TBW (total bytes written) lifespan to generally indicate how much volume it can handle before it typically starts to fail, usually only around 500 or 600 total drive writes. On a 1TB SSD, that's around 500TB or 600TB of lifespan. HDD spec sheets typically indicate maximum annual rated workload. I personally use enterprise-grade drives in my NAS, and they have a rating of 550TB/year, but that's total volume transferred, with a MTBF (mean time between failure) of 2.5M hours. What kind of drive you need depends on what you want to use it for.

[SIM-2502833]

I find HDDs fail more frequently in anecdotal experience. They don't like being moved around much.

[Blind2k]

So, of course, there are a lot of different anecdotes.
How much do you write and read data? Doe's the computer itself in motion when active?
HDD is a solid plate of data and a lot of machinery. The data is sort to say "engraved" inside the metal plates. Theoretically, if you will not write on it a lot and maintain the engine and internal hardware at top condition, the drive and data will be ready for action.
I had HDD that survived more than 5-6 years in good condition.
The HDD doesn't like to be moved when on. The plates will shake and might cause an error.

SSD is fast, light, and can be moved while on. The SSD saves information by injecting or removing an electron from a flash cell. With time, electrons can escape. The data you write today might(!)
not be the same you read in 5 years.

If you need:
Store data >> HDD is durable.
Playing games >> SSD is faster.
A mobile surveillance car >> ...
It depends on your needs...

[Kinin]

I backup my files to the external hdd. I move it so much and its lifetime not so long

[I ɴ ᴄ ʀ ᴇ ᴅ ɪ ʙ ʟ E]

my 2012 purchased WD Black Edition 2 TB died without many warnings 6 months ago.
So I'd say, usually 7-10 years.