I think relationships move at different paces. I know some people who are engaged and married so quickly it makes my head spin, but it seems to work for them. I tend to move at a much more conservative pace, and luckily my SO moves at about the same pace, so we’re very compatible in that way. Right now we’re in a LDR, next we are going to live in the same metropolitan area, but we don’t plan to live together, at least not right away. We’ve both lived alone a long time and don’t want to stress out the relationship too much. A good friend of mine assumed we were going to move in together right away when he moved to Chicago and was quite surprised when I told her we weren’t.
So my point is that no, I don’t think long engagements are silly, exactly, because really, I generally don’t know the intimate details of why any relationship moves at the pace it does. I may wonder “wow, they’re not married yet” but I assume they have their reasons. If they’re good friends, I’ll probably know the reasons. I know a couple of people at work who have been engaged for a very long time (not to each other), and though I think it’s a little odd, I wouldn’t describe it as silly.