[schreibr53]

I've read a lot about it. I understand that the olefin layer that binds the loops together loses its memory over time and sags when stepped on in the same location. What more should I consider before using berber to carpet stairs?

 

[Floorwizard]

if durability is the most concern then get yourself a Nylon Berber.
Small tight loops is best.

 

[ccarlisle]

Most "berbers" are made of polypropylene, a type of plastic, and therefore does not provide any potential for mould. That's why it is recommended in basements - and not everywhere. For water-based soils, it cleans relatively easily but for oil-based soils it's hard to clean. Polypropylene repels water but absorbs oils, so watch out what you spill. The weave of a berber being tight loops makes hot water extraction tough to use to clean it because of the reduced airflow up the vacuum hose...

And as already pointed out, its resilience isn't the best.