I always look for an engaging story, and even if you grab my eye with the art, you will quickly lose favor if you cannot give me a reason to continue (dressing a skeleton doesn't make the skeleton any less undesirable). There needs to be something intriguing or otherwise unknown, if I feel like an halfbaked idea is being presented, I'm typically not going to bother, as I would feel at that point someone just didn't try. It can even be a matter of relevance/interest in the topic.
The best way to lose my attention is inactivity, incredibly offensive behavior as a person or within a comic to such an extreme that I feel attacked as a person, or shoving your views mindlessly down my throat. (I appreciate @kurapikasuki 's work on No Future for such reasons, the interactions are respectable and two way street open minded, it's very welcoming in my experience). In short, if you don't respect your audience or even people of opposing views to you (I'm a fan of devil's advocate), or simply drop off the face of the earth, that may be cause for me to withdraw my support, but thankfully I have yet to meet any toxic people in Tapas, and thanks to how I instinctively avoid groups prone to toxicity, I hope not to start having bad experiences here.
Then again, I have had bad instances of long hiatus', and no doubt that contributed to this month's slow start. Thankfully my persistent activity seems to have been rewarded, as I'm enjoy new record highs on my comic as the month comes to its end. shrug that's just my thoughts on it.