Over there, ASJ asks whether the average Hassid is meant to involve himself in the complicated Kawanoth as laid out by the Ariz"l, or whether he is meant to pray simply and with great devotion. Rabbi Tal Zwecker brings down that it's a divided issue in the Hassidic literature, but in practice, the debate has been decided in favor of simple devoted prayer. (This is a very condensed summary, see the article for the full-length explanation.)
I'd like to put in a more unified perspective: Everyone agrees that prayer needs to come from a place of great excitement and simple devotion, there are many discussions and disagreements of when one is ready to take that to other levels of prayer.
Here's a different but related question: When is a relationship ready for the trials of marriage? Is there a time that is too soon, too immature, too naive? or a maximum limit that if you still aren't sure (or married) after a number of days, weeks, months, years (?) that you should move on?
Of course there are a million different answers to the question and the only person who could accurately answer that question is someone very wise and very close to the couple in question.
In the exact same way, prayer is a relationship with the Master of the World. When is the right time to take that relationship a step forward, when do you stop talking about how much you love eachother and start taking it to physical and/or biological levels? Yichudim are literally that, they are unifications of all manner of supernal realms beyond my limited understanding. The laws of Yichud should be applicable at least metaphorically to the relationship of a Hassid and HaShem. [Personally my Rav always told me I wasn't permitted to learn the writings of the Ariz"l as long as I was single. I still hesitate to get into them.] They are a part of the progression of the intimacy of prayer between one and HaShem. Hence those who delve into Kabbalah discuss the relationship of the Tzaddik and the Shechinah. They are appropriate when the Relationship between one and HaShem moves in the direction of a male-female relationship. For many people the Father-son relationship serves as a lifelong relationship in prayer with no need to progress, in a way this relationship is more pure, more devoted. On the other hand, a Father-son relationship doesn't leave room for the son to progress and grow in the same way that the male-female relationship does. It comes down to a relationship of receiving versus one of giving and receiving.
Physical unions (between man and woman) can be completely superficial, similarly Kawanoth performed without proper intent and devotion (heaven forebid) can be similarly superficial. Everyone is, I think trying to ward off such situations which could even be detrimental to the practitioner. On the other hand a physical union between husband and wife, for the right reasons and out of complete devotion can be a totally good and transcendent experience. Similarly Kawanoth can allow the relationship between one and HaShem to spiral higher to worlds previously unimagined.
In my lack of humility I would like to try and explain the Baal Shem Tov's words, quoted by R' Zwecker:
"He who uses the kavanna the Kabbalistic meditation intentions that he knows in his prayers, is only having in mind those meditations and kavvanos that he knows. However he who says the words with great connection, binding [himself on high] all the possible kavvanos and meditations are included! ...therefore see to it that you pray with intense devotion and concentration and excitement and surely you will succeed in enacting great things in the higher worlds since each word awakens above." (Tzavas HaRivash 14b and also Likkutim Yekarim 17d)The Baal Shem Tov is pointing out that in reality, the son gives to the Father so much more than the Husband could give to the Wife (or vice versa) but this is beyond the basic impression, beyond the simple understanding. I don't think any parent could argue with me. (Though I myself am not yet a parent.) The son doesn't know that the Father recieves anything from him, as the Husband knows about the Wife.
I think it is actually a full circle. Our relationship with HaShem is meant to go through the stages, starting with Father-son and eventually to Husband-Wife finally leading back to the Father-son relationship with the renewed wisdom to appreciate just how much a child gives to their parents.
This can be seen in the life-cycle. In old age, we (heaven forebid) lose our parents, and HaShem is the only remaining parent we can turn to.