How Long Should An Ideal Steady Relationship Last Before Marriage?

I have come across people who met their spouse and under two weeks they were pulling marriage strings, and i've seen others who after like 6 years they finally tied the not. From experience i don't think a working man should have a steady relationship that will last for more than say 8months, because before then you are either preparing for marriage (searching for someone to settle down with), and also searching for the right partner (and not screwing around with every babe). So what do you guys think should be the appropriate length of courtship?
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