Referee reports not coming
As always, one needs to look within oneself. Ask yourself the following questions:


How broadly interesting is your oeuvre? In my experience, difficulty in finding a referee often indicates that the field is very narrow, and the editors are looking for a referee to check whether a paper is a breakthrough in the narrow field. Otherwise, the paper is rejected.
How well-written are the papers? Especially the introduction - if the prospective referee's eyes glaze over when s/he reads it, s/he probably won't want to referee the paper. I realize that the author is not the best judge for this, but show the paper to a friend.
You can usually get papers published quicker if you submit to a lesser journal (and I assume that it is ALREADY published on arxiv.org). The optimization problem (quality vs speed) is for you to solve. From a careerist standpoint, the journal weighting is very nonlinear: a single paper in Annals of Math is worth essentially an infinite number in, say, PAMS (no insult meant). If you are already established, then you might not care. If not, you might.


Just one man's opinion (though I am active on several editorial boards, so the opinion is somewhat informed).