The down side of that is that I believe my INFJ friends also look for time spent and continual interaction to determine strength of friendship, and I'm not very consistant with these things. I think that I have hurt their feelings alot, just through those fi/fe differences, which is a dam shame because I really do hold a very special place in my heart for them.
+100
I think Huxley has worded it perfectly that the biggest problem with ENFP-INFJ is that INFJ is prone to be clingy to a potentially rewarding friendship where as ENFP would rather to keep a certain amount of personal space and distance.
I've seen ENFP seem to be very compatible among ENFJ and ESFP since they seem to have a busy social life and that probes ENFP to continually keeping in touch with them.
This is quite an interesting topic and I hope other types would infuse their ideas of my observation, especially if they think that my implementation may seem to be a bit off.
The thing about ENFP-INFJ is that I consider this union is rewarding as long as you keep it as a pure friendship but romance (Starryknights may have more insights about this claim and I hope she would elaborate her ideas here).
When it comes to both types, I think both are quite self-critical and challenging to themselves, but in opposing spheres. INFJ tends to seek challenge to promote personal growth based on their inner-self. A case in point is when we felt we lack of certain admirable qualities, we tend to dwell on improving it. Thus sometimes it results in mirroring from others. Whereas for ENFP, they tend to seek validation from the external world. Thus they invest heavily on observing people within their circle and really work their best on adjusting their personality to compliment others. And perhaps that makes them to become one of the most popular type among all.
The problem is when INFJ pays too much attention on emotional investment by paying extra attention to those who they've handpicked selectively. As Fe empowers INFJ to show their inner-rich feelings and sentiments when they felt they're being appreciated by others with a deep level of understanding. This, however, can lead ENFP to feel less challenging to invest their radars on INFJ as ENFP can be so effortlessly intune with anyone once they've given a chance to get to know someone. So once INFJ reveals or open up too soon to ENFP, all the curiosity and motivation is dissipiate for ENFP and they will not pay the same amount of time and effort to socialize with one. I think this has to do with their genuine nature and challenge of being a people-pleaser. To keep ahold of ENFP's attention, one has to be constantly interesting and hard to read for them.
Perhaps when ENFP and INFJ gets to share deep and insightful topics, that's when both types will become fascinated to learn from each other because they tend to have very different views regarding to the same topics. Though when INFJ decides to open up, they tend to open up too much and a little too fast, this will lessen the excitement from ENFP for putting an effort to get to know INFJ more as they're already super-busy with their endless strings of personal ties and connections from various groups.
I think keeping a certain amount of distance of personal space and private/personal information is what makes the dynamic of ENFP and INFJ works in amiable harmony.