How long can you stay engaged before you get married or can an engagement last forever without marriage?

I think that depends on the couple in the relationship.You need to have a serious talk about your goals as a couple. If you're worried about "losing" something by getting married;maybe you should reconsider what you really want.If it's really right, then marriage shouldn't change it, in that way. It really depends on the two people involved and what they want. Don't let anyone try to tell you there is a right or a wrong way, just do what is right for you both.