I was the one who started the off-and-on thread, years ago -- it was then pointed out to me that I had a pretty classic boomerang, rather than an off-and-on, who would have contacted once every few months, possibly.
So I'm afraid what I thought was an off-and-on wasn't, what I was seeing was more of the cycling that is described. He would come towards me, then run. This has been repeated in cycles of varying length for many years now.
I've never had a clinger, at least not in the sense that I think RCR defines it as: as one who wants to remain married while having his other life as well. Trouble is, he's never been able to articulate what he wants, or at least it changes with whatever else is going on in his life.
Mind didn't start d proceedings until nearly 5 years in; he also never finished them, although those threats come up now and again.
Mine has opened up at various points in this mess; that gives me some insight, then he runs again and it hurts again.
The pros of this are that you learn better to deal with it all; you learn to respond rather than to react, all that.
The cons are that no matter how hard you work to detach, let go, surrender, you always have something to deal with. Right now it's a combination of monster and more avoiding behaviours, which is very weird. And the odd bit of "normal" mixed in, just to add to the confusion.