What are the pros and cons of a long Engagement?

In my sociology cl we were reading about a study that shows that the longer an engagement is, the more likely they will have a divorce. An engagement over 3 years had almost a 70 percent divorce rate. It has to do with pretty much being in limbo for however long and being almost married, but not really, and the stress of planning a wedding. If you don't have a choice though, then just make the engagement process as easy as possible. The truth is though, that a longer engagement does not really make it easier to plan because vendors usually do pricing by the year and you cannot reserve some things so far in advance. Planning a wedding more than a year in advance is difficult because you can only reserve the venue that far in advance.