Depends on the tank and how it is wicked. I just changed out the wick on my Aqua today after using it a week and filling it over 14 times, probably more like 30, can drain this bad boy real fast at the level I vape at. I don't get no backwash, and when I am out of juice it is drained dry. So I only rinse it down with hot water when I do a wick change and or, changing out the flavor. With the iclear, would probably be a good idea to rinse it out every other tank or so. This will keep it cleaner, and help extend your coil life by not subjecting it to the crud build up that you are getting with your tank.
Since most of my tank system are all stainless steel, I never see the juice, and since they are all bottom coil rba's wicked with cotton, when they run out of juice, there is nothing left to drain out. I usually get a week or two between wicking, depending on how much I am using them, when I do re-wick I always tear them down, washing out all the parts with hot water, dry burn the gunk off the coils, re-wick, saturate wick with juice, assemble and fill.
When I used a protank, I'd rinse out the tank every other fill up, and change the coil head when vapor production was down. As you become more familiar with you equipment and the taste of the vape, you'll know when your atomizer needs servicing by the reduction of wicking, taste of the vape and reduction of vapor. There is not set rule and every thing depends on your equipment, preferences and how much vape quality reduction you are willing to be satisfied with before servicing your atty.