I think to enter into a relationship knowing there will be an expiration date speaks more to your character. Almost sounds like "I'm with them unless something better comes along or their shortcomings become more than I want to deal with".
If you genuinely love someone, you will stand by them, work on any problems, and remember that you chose to build a future together. Given that the divorce rate in my community is less than 1% we're probably doing something right.