I think it took about a month for me to get fully trained. The critical day was the first day of a week long ride. Every time I came to a new town and had to stop, I slowed to a stop and fell right over. After 3 times, one of my riding buddies assigned himself the task to remind me at every stoop that I needed to click out. Halfway through the second day, he stopped warning me and I had no more incidents.
Hang in there. It's not the pedals. You can teach an old dog new tricks, but sometimes it takes a little longer than you think it should.