How long should you stay in the 'talking' stage with someone before starting a relationship?

So I've been talking to this guy since early July so about 2 going towards 3 months. We have both made it clear that we do not want to and will not talk or mess around with anyone else (we basically have all the elements of a relationship except the title). BUT we have also both made it clear that if one of us wanted to mess with someone else we could do that and technically neither one of us can say anything about it. Recently we had a talk where I asked how he would feel if I started talking to someone else and if he trust me he told me basically "people are gonna do what they want to do and there's nothing I can do about it it would just kinda be like that's messed up..." And he said he would care if I started taking to someone else. Right now he just calls me his sweetheart and I kind of just refer to him as 'dude' or 'bae' or 'my honeybuns' when referencing him in things like a Facebook post that reminds me of him and so forth. I don't want to tag him and parade like we have this relationship when I'm not really sure what it is yet. Even though, we're pretty much exclusive both by choice (and he's always assuring me he's not gonna do anything) we go on dates, sleep together (both sexually and non sexually) we talk everyday through the entire day (literally). How long would you go without trying to define the relationship? I want to be boyfriend and girlfriend but I don't want to pressure him into feeling like he has to feel the same or is gonna hurt my feelings if that's not what he wants right now. But I also don't want to end up like my last relationship where we were talking for 6 months and things ended really badly because we saw we didn't have future together really. When is a good time to bring it up? How should I bring it up without sounding to heavy and how long have you or would you indulge in the 'talking' stage?
How long should you stay in the 'talking' stage with someone before starting a relationship?
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