I started vaping with the eGo-C system a couple of years back and used that exclusively for a couple of months. I found I had to dry burn my attys every 3 - 5 ml of juice to keep performance up to par and to avoid losing attys early. Letting an atty go too long and get too gunked up makes it really hard to clean properly.
Here's a good video of how I used to do it. You have to be careful not to hold the power on too long when dry burning or you'll melt the coil (pop it) and that atty is toast. It happened to me once and then I understood and it never happened again. I found I had to continue the dry burn process until all the coils glowed or the cleaning was not complete. If it takes a while I used to let it cool down a bit before continuing.
A lot of people didn't like eGo-C attys. I found them very good for clean taste and vapor production, but very maintenance intensive and expensive compared to other options out there. I use RBAs and RDAs almost exclusively now and am a bit behind the times with the latest clearos available today. I can tell you though that once I discovered CE4s and then Vivi Novas I left the eGo-C attys behind.
OTOH they work and they got me off cigarettes
. Hope this helps a bit. Best of luck with it!