What parameters define a bad strut?

Doing my first DIY shocks/strut replace...

...and I am beginning to wonder if the typical "quick and easy" diagnostics are sufficient.

Lots of people say either or both of:

A) Does the car bounce if jostled or goes over a big bump?

B) Is there evidence of a fluid leak from the strut?

The ride on our 2011 has just felt off a bit. No obvious issues.

I just pulled a rear strut and compared to a brand new one.

The primary difference is in how long it takes to re-expand of I manually push in the piston while out of the car. Obviously not an in-car test

New: around 10 sec
Old: around two minutes

Other than that, the old one displays no failure symptoms.

Thoughts?

 

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