Is it better to be straight up about feelings of 'forever' in a relationship?

I am not someone who believes in marriage or the concept of being together forever, I think its a great concept, and possible, but most of the time is unrealistic. I feel right now, that I would like to be with my boyfriend forever, and even though I admit we most likely will not be, its enough that I want it.
My boyfriend and I were talking about this the other day very casually and we were just like, “can you imagine if we were together forever? That would be awful”. We always talk like that and say things like “when we break up…” but neither of us have any desire to break up anytime soon and we are very serious.
All my friends say this is really weird and why bother being with someone if you admit your going to break up, i find this odd…Are you supposed to just deny it?
I think that it makes more sense to be happy with someone until your not happy anymore, and know that day will eventually come. Is this a weird way of looking at things?