I had a little problems with them at first. The first Joye 510 carto I filled with RY4 I tried to vape almost right away and I just got a burnt taste that never went away and I vaped through it till pretty much empty cause I didn't wanna waste it but I tossed that carto after only 1 fill. I tried again about 2 days ago and let it sit an hour before touching it and I'm getting big clouds and great flavor. I've refilled it several times since and always give it at least 20 min to sit and it's still working great.
I don't think I've ever had to let mine sit, but I tend to follow Coz's method and slightly overfill and suck out the extra from the vent chamber. It certainly can't hurt to let it sit though.
I've also found that you can get a bit more life out of them if, before refilling, you drip straight PG into the vent chamber and blow it out. When I do this, I see little flecks of carbon on the tissue that I blew it out on.
I tried the eGo cartos this week too. I've been getting slightly less vapor, but they're very much similar to the regular 510's. I've already gone through 2 of them though. One because I put it in my pants pocket while I was doing some plumbing work and it melted. The other because I screwed it on too tight and the threads twisted off of the atty.
I'm still using the E2 cartos as drippers, and they're still working great - I haven't had to trash any of them. I don't use them often though.