Has any one noticed any performance issues when reaching roughly 1200 products / 2500 customers - a client if mine has been asking me as they are saying the diet is running slowly (front and back end).

I know most carts say unlimited categories / products etc but with Zen Cart what is a more realistic description of the limitations. The client wants improvements otherwise wants me to move to other software.

No addons have been installed although the theme is not the default - pretty much a bare bones site with just branding changes.