I had one coffee flavor that killed an atomizer in one hour. Killed it! Didn't just clog it.
Watch out for thick, dark juices and sweet juices and, of course, coffee flavors. Now, after saying all that, some thick, dark juices are ok. Some sweet juices are ok. And, some coffee flavors are ok. It just depends.
Sorry, that was pretty useless, wasn't it?
I'm in search of the perfect coffee flavor. That's a big part of why I DIY. Good coffee flavor without gunking up, or even killing, cartos. I got sick of paying money for junk.
I suggest that you ask around and read the E-juice forum. There really are some great juices out there. It's just that I gave up on buying premade juice before I found that out. And, now I'm used to saving all that money!