Marriage Proposals; How Long Is Too Long To Be Engaged?

The society just has a way of pressurizing people into doing things, especially when it comes to marriage issues, when you're done with school and have a job, the next thing you'll hear will be '' Ahn ahn when will you bring your boyfriend or girlfriend for us to see, when are you guys getting engaged, when is the wedding'' it's an endless cycle.
Now speaking on engagements, how long should a couple be engaged for before the wedding and how long is too long?