I have one or two, where I'll just click on them to remove the update-notification.
I'm not ignoring them so much as I'm letting them update a whole bunch before I sit down and read a bunch of pages in one go - some comics work better like that. I believe my own comic does, because I see that pattern with my readers - some of them read page by page, while others let it go a couple of weeks and then read an entire chapter in one go.
If one of the comics on my reading list stops being enjoyable - if I don't like the way the story is going, or if the characters stop being interesting, or whatever - I'll unsubscribe.