I'm really not sure, to be honest.
Yes, I had thought for a long time I'd need to be with someone who is EII, IEE, or perhaps IEI because I met some exceedingly cool IEIs.
And it might seem ironic to say what I said AFTER having been with an IEE, but, I say that because what is really making the relationship work isn't related to socionics at all. I thought it would be - I thought it would be making a big difference. I thought that it would come down to socionics very much, and spent time wondering "well, would this work better with my dual?". But what has prevailed are other aspects of a relationship; things that would override whether or not it was my dual; things that would, if more negative or not present, would obliterate any significance duality had.
I suppose I'd say, socionics is useful for selecting the mental aspect of a partner, but it certainly isn't useful for picking other aspects of a partner.
I'm also somewhat wary, coming out of a socionics-interpretation intensive situation, that one's knowledge of socionics can be problematic in a reationship especially if someone doesn't know ANYTHING about it. Because socionics, like this forum, can train you to think in certain ways and interpret things in certain ways; you've seen it on a profile and talked to someone of that type about it, so it must therefore be accurate and the assumption you have must be more than an assumption, right?