I only use 100% VG juices with my eGo-C and have no problems. I do a few dry drags at the start of a new tank to make sure that wicking is well established as indicated by small bubbles floating up towards the mouthpiece tip, although sometimes with really thick juices I'll also need to tilt it back and forth a few times and/or rap the cone against my palm a few times to dislodge the air bubble that sometimes get stuck on the atty spike and blocks wicking. After that it's usually mostly a matter of adjusting drag strength to the sweet spot between flooding and dry hits, although a few times I've also had to adjust the wick to improve wicking because I was having to dry drag more often than I wanted to (see this
short video for an explanation and demonstration). As with dripping and probably any other juice delivery system, you do need to have a certain level of awareness about an impending dry hit (e.g., reduction in flavor and/or vapor production, slight metallic taste) and take preemptive steps, e.g., a dry pull or two.
As for atty longevity with VG juices, my experience is that seems to be mostly a function of how dark and "gunky" the juice is. I've had attys last for well over a month with a clear, clean burning VG juice like Ecopure while others gunk up in less than a week or so with really dark juices such as coffees and chocolates.