Confident? Sometimes. . . I'm more secure than anything else. I think that if anything ever did tear my marriage up, I would fall over and die purely from shock.
As for achievement, I don't really see it that way - S.O.C.K.S., as I like to say
(which is phonetically spelled 'it is what it is' in Spanish).
There's times where there's 'couples' going on - say if I'm at work and their schedules have them home at the same time, or sometimes one pair of us or another will find the time to do lunch, that sort of thing. More often than not, there's at least two of us available to do something on a weekend or in the evenings. When all three of us aren't busy, we try to go and do something.
Three people lazing in bed on a sunday morning is just the same as two, only moreso - 'cept for the gazing-into-each-other's-eyes thing - you'd have to go cross-eyed!
All in all, it can be comfortable and secure - there's no need for 'coping' when the others are doing something - sometimes it's nice to have some alone-time. Of course, if any one of us were a jealous person by nature, it wouldn't work very well at all. He's got a little bit of an advantage, though, because he's the only male involved. To him, the relationship between she and I is completely different than his and mine. I would be happier if she and I could be closer, but somehow, it's not working right, and there's a limit to how much time she and I want to spend together... thus the feeling that it's not going to be a long-term thing.
Edit: S.O.C.K.S. is not a translation, it's a pronunciation! Eso si que es! {/dork}