Container gardening

 How often should a commercially-available potting mix (i.e., a soil-
less growing media) be COMPLETELY removed and replaced with new
commercially-available potting mix?".  (I'm not referring to "dirt").

 
It's really a matter of soil pore space and salt buildup.
As the soil ages coarse organic material gets smaller and smaller
blocking air exchange with the roots.
Once a year should be adequate for ornamentals.

 
Thank you for this informative reply.

 In article  gcotterl@co.riverside.ca.us says...

I make my own mix out of pine bark fines and other stuff.  That mix
lasts me two years before being replaced.  But, even if the mix isn't
being replaced that year, the container still needs to be dumped and new
fertilizer added and then the mix goes back in the container.  Check out
the container gardening forum on gardenweb.  There's a lot of useful
info about containers and container mixes.