Hi, Daross…
I used to rosin once to twice a week when I was playing shows daily…these days, I don’t play much, so I don’t rosin much…if your playing a couple of hours a day, you’ll find that your rosin will need to be refreshed fairly frequently.
My rule of thumb – soft/wispy tone means I should re-apply (this is also a good indication that your bow might need rehairing)….biting/harsh tone means I should maybe back off on the rosin for a bit.
Hopefully that’s helpful!