Daily. And I don't mess with meds or salt. I wouldn't mix meds and salt, either. They both do basically the same thing. I just stick with heat (86) and I'm usually good. Meds are a waste of money, to me, as I've lost fish 100% of the time that I've used them. With heat only I've only lost fish once or twice (out of 10+ times treating it, and no fish in the last 5 times).
But, daily water changes will keep the fish happy and the ick levels low.