There are many shades of poly
and all those shades can be completely different light or dark colors depending on the flavor of polyamory you choose as food to feed your soul.
No, the pain and negativity (jealousy, insecurity etc...) will NOT always be there, as those are not the fruits of a healthy living with healthy relationships
As you are learning to live your life in the manner you choose -- some call it an "awakened" life -- the progression is a series of small steps, as there is no elevator to carry you to the "LIVING"
however there have always been those who will sell you a ticket, or provide you with instructions on how to build an elevator to magically carry you into a LIFE that Is real, as opposed living while still asleep.
Often people refer to the stairway as "baby steps"
It is not an easy journey, and on the way you will likely find out that -- no, at this point in time knowing all the details will harm you -- however in order to do that requires that your trust, or faith be in a worthy spouse, that his behavior as well those who have a relationship with him are behaving in ways that are respectful and with genuine concern for your well being
as that is the only behavior that includes details that you should eventually be in a place where knowing every detail no longer harms you
this is an important because it is the fate of all human beings to understand consciousness, as we are capable of "knowing" everything, and unless prepared that will be too much to handle for many people
as it takes a hell of a lot of practice to be able to live with the "truth"
it takes a hell of a lot of practice just to be able to recognize it (the TRUTH) let alone to be able to handle the LIVING of it (LIFE)
We are humans, nobody is perfect, it is how we handle our imperfectness that counts. Hopefully your husband will understand that his isolating himself is not letting you in, and the TRUTH is that LIFE is a shared event.
Needing moments alone is something most people require, but not letting you know a time frame of how long he is going to shut you out is not taking a moment alone, you are his spouse and letting you know "he isn't shutting you out" is not the same thing as saying three nights or a week.
Which is not healthy behavior for spouses, unless he knows you desire and consent to that type of behavior.
For many people who are in serious committed relationships, in order for your relationship to survive, the "unknown" is usually traveled through together and often little things like shutting you out so that you are "alone" without knowing the time frame, can in many ways create "unknowns" that their partner has more emotional trouble than is necessary
maybe what is more important than knowing when your being "alone" in the same house is going to end, is that when he emerges he is willing to honestly talk about whatever he cannot share with you at this time
because that is what does the irreparable damage to a relationship, when all those seemingly small short lived hardships are for nought, because the circumstances that led to them are never dealt with
know you are not alone, that all people who appear to have "made it" and are "Poly" are only proclaiming each baby step along their journey, some of them without even realizing their stairway only leads to the top of a cliff