I want to know what determines the slowness (recovery time) of
viscoelastic foam (temperature sensitive memory foam). Is it the
density (this is what most manufacturers claim), open-cell structure,
temperature, its chemical components, manufacturing process?

Some manufacturers say that quicker recovery to original shape means
the mattress adjusts quicker to a new position when you move in bed
compared with other higher density memory foams.

I'm most of all interested to know if these quicker to recover
viscoelastic foams are better or worse quality than slower
viscoelastic foam especially in terms of lifespan and durability and
knowing what determines recovery rate (or rate sensitivity) it will
tell me that.

I have tried many memory foam products out at retail stores like
Wal-mart and Target. They seem to bee very soft and have a fast
recovery time which almost seems cheap. The expensive tempur-pedic
memory foam has a slow recovery that I have tried in stores is almost
too slow. I ordered one on line from Cloud9 Bedding and it was a 5.3
Cloud9 memory foam. This seemed about right and had a slower recovery
than the store brands and slightly faster than the Tempur-pedic so you
would not end up stuck in bed. The website was
www.wholesale-memory-foam.com and carried mattresses, toppers and
pillows.

The recovery rate of memory foam relies on two very important aspects
of the memory foam itself.  The density is important because the
memory foam will last longer if it has a density of at least 4 to 5
lbs.  The other important aspect is ILD or "load deflection".  This
gives you an idea of how firm the foam is.  Tempurpedic uses a 14 ILD
memory foam.  The importance is that a higher ILD will also lead to a
slower recovery time for the memory foam itself.  We offer a 10 ILD
memory foam that recovers a little faster than Tempur.  We also offer
a 14 ILD memory foam that acts like Tempur material.  Using the ILD
rating and density together you can get a better idea of what you are
purchasing.  In the meantime, visit us at
http://www.memoryfoamfurniture.com.