I'm not officially dating with my wife, just one blind shot and next few months I married her. It's funny, back before my count is kind of high, but my wife is kinda different take back before. So we are not officially named couple, just close friend while waitiing for wedding day
5 years. I waited way too long to pop the question and it caused some issues. I finally proposed one month before we moved to a new city/state together. I figured that was the best time to show full commitment and finally do the damn thing. We're coming up on our 9th wedding anniversary this year.
I think waiting a little on the longer side is best--3 years or so--to really know the person and see how your relationship is after the honeymoon period is over. But I got comfortable and procrastinated. I'm glad it didn't cost me the relationship. She was patient with me (but not very happy about it). She knew it was going to happen eventually but 5 years was definitely too long to make her wait.
Dated for three months before getting married, but we'd been friends for many years before that. I knew my current wife before I knew my ex wife, and I was married to her for three years so I've known my current wife at least twenty years now, been married for fifteen years, sixteen in September.