Wow these were all really good posts, thanks, it really did help.

In my personal case I and the other person in question are negativist introverts and I could definitely sense the lack of a spark and possible trouble in the future, plus the fact that I gradually feel worn down by them after awhile and need my own space.

On the other hand we do get along really well and have tons in common, so I've concluded that for now there's nothing wrong with an activity relationship if there are no duals around. BUT, if I ever meet a dual that looks promising I am so jumping on that bandwagon!