Let's look at a hypothetical situation to illustrate this: There are two couples, couple X and couple Y. Both these couples have been together for the same amount of time. Couple X has frequent conflict, couple Y has never had one. Who among the two has a healthy relationship?
If you're answer was couple Y, you're wrong. It's impossible for two people who're together to have no conflict at all. In the case of couple Y, it's most likely that one or both partners is not forthcoming about problems. The needs of one or both partners isn't being voiced and hence not addressed. So how you communicate your needs and manage conflict is a significant pointer.