Yes, I believe so. I think of a previous relationship ended on a healthy and mature note as something like an article of clothing or a favorite toy you outgrew. It's not really something you can use anymore, but you hate to throw it away.
Sometimes you reach a point where you realize it is no longer moving in the direction you wish to be traveling. In some cases (actually, probably most), I believe it takes some time before the friendship kicks back in gear. It seems very normal for one person in the relationship to not be on board with the separation, but eventually, they understand. Some people find that they actually make better platonic friends than they do lovers.
I also think there are many situations in which a maintaining a friendship is nearly impossible, and at times, unhealthy. But with two level-headed people talking about what's best for their future, and keeping each other honest, it is very possible.