There's no sense in being overcautious, treat every one like they are expendable. Post to them all as often as you would like to post. If you lose one, then you know which ones are picky.
Various web2.0s on the list are picky over what niche you use, whether you're using it for seo purposes or by fluke they just happened to be reviewing your blog on a bad day. Ultimately everyone's experience is going to be different, and its better to just put it up and move on rather than worry about whether it will be deleted.
I like to stick one up, and if it happens to last a month I make it a tier-1 and start building backlinks to it.