On Oct 12, 10:45*am, GARY wrote:
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.