I only have experience with the Star Dust, but I'm willing to share that.
The answer to your question is (like the answer to any cleaning question) when it is dirty. When new, they can go for many refills before cleaning. It also depends on the
e-liquid I am using. RY4 is thick and dark and the wicks tend to filter as they draw, so naturally they clog up faster with these. My
tobacco flavors are thin and light colored (no dye) and can go for more refills between cleaning.
After about 3 weeks of use (for me) the RY4 ones need to be cleaned after nearly every use. At about 5 weeks I have been retiring them or only using them for lighter juices so that I don't get dry hits.
For normal cleaning I just add about a half mil of distilled water and shake them while blocking the ends. I repeat about 3 -4 times. I also brush the wicks with a needle to make sure they get cleaned well, then I spread the ends of the wick so they don't dry bunched together. I let them dry over night and then do a quick dry burn to make sure all the water is out of the wicks.
About once a week, maybe longer, I let them soak in distilled water (a shot glass works well for this) for an hour or so. Then I use a needle and syringe to "Pressure Wash" the wicks and spray into the center from both ends. I let them dry and do a dry burn to check the
coils for build up. They usually last me about 5 weeks or longer (I know they could last longer) and I save them (retired) as I may want to rebuild them in the future. If something better comes along, I may not want to!
Relax! Enjoy!