To be honest I use to do this weekly thinking it makes a difference. Tried the rinsing method above, boiling, surenge method, etc. I did however find that sometimes the wadding just gets shrunk and makes the draw like milkshake hard.
Now I just pick 1 flavor for that cartomizer and stick to topping off or complete refill. I usually inspect it at refill and if it looks toasted i toss it, or if performance reduces. This way I find that they last much longer.
GL to ya!