Seven months is a LONG time to hang in there with one agent - if, indeed, you were the only agent they were working with. Had you written offers on their behalf, and if so, how many?
A LOT of buyers in a market like this start to develop a sense that they'll be more successful in their negotiations by dealing with only the listing agent, and to a certain extent, that's a valid assumption to come to, especially when the agent they've been working with has not been successful in getting their offer(s) accepted. That is very frustrating to a buyer who's been making LOSING offers for 6 or 7 months, while watching prices go higher every month.
In addition, most listing agents are aware of this, many of whom are just unscrupulous enough to promote their listings in such a way as to "snag" those potentially disloyal "clients", by holding open houses, ( HOW DARE THEY?) or, tactics such as offering reduced commissions to cooperating agents. ( There is a growing number of new listings popping up offering less than 2.5%, for example, and it's not like they're just with short sales.)
So, the moral of the story? The same one I've heard for all of my 36+ years in real estate. It's better to concentrate on getting listings, than it is to work primarily with buyers. And, by the way, as much as it pains me to admit, I lose such a "client" in such a manner every couple of years. You'd think I'd get used to it, after 36+ years, but it still hurts every time - just like it has hurt you, Julia.
Obviously, there is something to be said for only working with buyers with a written buyer's agreement. If they won't agree to sign one, after a week or two of building trust, they MIGHT be the kind of "clients" who will end up hurting you, somewhere down the line.