I'm unclear as to what would be the definition of a "good" marriage. I've met just about every type combination in long-lasting relationships but duration is certainly no measure of happiness or contentment. I would label most relationships including duals as cohabitants who are dependent on and or habituated to one another but I've seen very few where both seemed truly happy after say 20 years. As well, very few were romantic beyond the first two years. I define a good marriage as remaining respectful and helpful to one another but this is often done while living separate lives.

a.k.a. I/O