Dosing ferts depends on your lighting and plant growth. When you first start dosing you might dose once a week with a water change, but as all your plants begin to grow, you may need to dose 2-3x a week.
More lights and the addition of CO2 usually means faster growth, so dosing has to kept in line or you will see some plants turning yellow or melting. People with hight tech tanks who dose daily tend to do a larger (~50%) water change weekly to "reset" some of the water parameters. This way they don't have to fine tune their dosing.
I tend to dose 2-3x a week depending on if I remember or not. I run CO2 but keep my lights under 2wpg so I have a little flexibility when it comes to dosing.