If after three dates you haven't slept with him/her, dump him/her.
If after three months you haven't said "I love you," dump him/her.
If after three years you aren't married yet, dump him/her.
I don't prescribe to or proscribe this schedule but its quality lies in its simplicity, because the reality is much less succinct (if funnier):
If after three dates you don't know anything about him/her, you're just a lay.
If after three months you aren't talking "love," you (i.e. she) will start fighting.
If you keep at it and are with them for three years but aren't married yet, you're going to get divorced whenever you do decide to get married (which you will, because you won't have the courage to dump him/her).
Here's the new truism.
Go on three dates with someone you loved at first sight.
In three months, give them something small but valuable. A word, an object, a gesture.
In three years, go back on a date with this person. It's cheaper than a wedding.