I'm an ISTJ female dating an ENFP guy.
Our chemistry and attraction has been perfect. I'm very shy and take a while to warm up to people whereas he's very popular and knew he liked me the instant he met me, and made that very clear. Our conversations are great and we spend a lot of time together. We're fascinated by how different we are and can talk for hours.
I'm just really worried that he'll realize I'm nothing special and get bored of me. He's constantly doing things, befriending everyone, while I'm very introverted. I look for loyalty and stability in friendships/relationships so I'm scared of getting too close to him. How quickly do ENFPs get bored of people? Are they flaky or loyal?
I would say that you need to understand those professions of deep love, so early and so deep, are likely true for the moment but as quickly as they come they can also fade, although the ENFP will "work" on the relationship when they fade but through their E and F function, which sadly comes off as a very indirect and passive-aggressive way to work through relationship issues with an INTJ or any IT.
Note these are just processing types, a mature intelligent person of any type will recognize that different people process and show love differently. The real test is how he resolves differences, can he connect with your calm approach to resolve disagreements or is there a level of emotion (a level that can ramp to threatening the relationship) that prevents the kind of discussion an INTJ can have about a relationship.
I say this from being in a relationship with an ENFP woman. She was professing deep love and my being her soul mate after only a couple weeks together. It made me nervous too, but I went with it; we did have great conversations and chemistry. After about 6-9 months I truly believed it as well and started building a life together. It was a wonderful year, but eventually she could no longer live with my "lifestyle". Caveat, nothing odd or really boring just an INTJ guy with kids so her not getting 100% of me 100% of the time was getting her down, where I live there are not shops literally 2 blocks away, they are a half mile away, and even though we got out and travelled almost once a month, I still would like a to spend a couple hours a week introverting out which I think she took as rejection.
ENFP also like to please and hide there selves to do so I found out. She revealed, after about a year, that she basically wasn't upfront about what she wanted, but only after passive-aggressively trying to "tell" me. This after our weeks of initial conversation about how we were looking for communication, to say what you feel and think and not hold it in. Despite picking up on her signs of discontent and asking her what is wrong.
I made a point to be much more verbal and effusive than I normally am. Yet she always seemed to think I was holding things in when I was not, I was content, just that INTJ calm, because she was wired to talk and express emotions often she never got it despite talking about it with her. She didn't cheat on me. She did end it in a kind of underhanded/passive way, then got upset when I did not pursue her after. Despite the ENFPs vaunted ability to understand other's feelings, I never saw this. They understand feelings, and how other E's and F's express them, but not everyone. Especially not I and T types. It's a real blind spot for them and they think we are unfeeling because we don't emote the way they do, when actually our feelings are much deeper. Although we don't offend or hurt easily, if you betray us emotionally we also do not just forgive or have a dramatic argument and all is good (or at least not more than once or twice), rather we just move on.
Bottom line, if the good times are good, go with them, as long as you can resolve differences, and argue fairly that is the key to any long term relationship. Don't let him guilt you for your introvert tendencies or make you feel inferior because you do not emote like he does.