I guess it depends on how you think it is extending the life. If you are out of space -- maybe, though moving things other than the OS there would be better. If you are out of horsepower, I really doubt that hanging a fast SSD on a slow USB cable will help. There's also a much higher likelihood of corruption like that (e.g. you accidentally unplug it while working).
Most computers of that vintage will have sata drives. SSD's can be SATA also. I would think you could swap the physical drive inside the computer for an SSD of the same form factor (but maybe more space) and end up with a much faster setup plus space, for only the cost of the drive (maybe plus someone to install). I did that on an old Dell latitude, took all of 10 minutes for the hardware part.
If I did that, I would also re-install windows from scratch, as a sort of house cleaning. But you can clone the internal drive to the external SSD and then swap them physically.
If thinking of doing that take that particular model and do some internet searches, it is doubtful you are the first, you might find either instructions, or issues, in doing it.
But again -- it depends on what problem you are trying to solve with the SSD. You might want to describe the problem you have, rather than starting with the solution. Though starting with the answer and seeking out questions made Alex Trebek wealthy, I guess.
