Thank you.
No passes made, no words of love, no promises for the future, and I'd start to wonder if maybe I'd found that rare man that doesn't want it AT ALL, even after marriage.
A time limit of six months may be a little short (though, perhaps not for a 33-year-old ;), but in general I totally see your point.
I gave a Sweetie a diamond ring four months to the day after we met. About four months after that, I gave her a matching gold ring. That night, we were too tired to do anything. But after that...
Still, for some people more time may be needed. I wouldn't fault a woman who, after five months, announced that if she didn't have at least a schedule, if not a ring, she wasn't going to stick around forever.
Note that I wouldn't fault a man for wanting to wait until after specific events before getting engaged. For example, if they were planning a trip to meet her parents, I wouldn't mind him waiting until after such meeting to make his proposal, even if it was more than six months after they first met.
If the woman asked for a commitment out of the blue after six months, and dumped the guy because he wasn't willing to promise within five minutes that he'd marry her, I'd blame the woman. If, however, she game him a reasonable timetable to make such a decision and he refused to either make it or negotiate a different but specific timetable, I'd blame him.