Ive never tried the whole open relationship concept myself however I did work at a nudist and swingers resort for many years. I always asked the couples that had been married many years what made their relationship so successful. The response "everyone gets bored and wants a different flavor ever now and again, it's not the cheating but the lying about it that kills relationships. Sex is just sex and the love of spending your life with someone and understanding each other's primal needs is something totaly different.

Like I said I havnt got there yet however I certainly wouldnt rule it out of future relationships.