I think it varies with each of us. I'd say we all have lingering symptoms after the worst go away, and the lingering ones maybe require more time, which we never manage to reach.
I think POIS actually does physical damage in some areas, like maybe joints and / or digestive tract, which require more time to heal. So maybe those might take a month, so we never abstain long enough to know.
But I think there are some who's worse symptoms last longer. Especially it seems that some with cognitive symptoms primarily tend to last longer.
In my case (with normal POIS sessions) my cognitive symptoms only last about 2 or 3 days. The rest are physical. But for others their cognitive symptoms last longer, and in some never go completely away.
Of course few of us go more than 2 or 3 weeks between orgasms, so it is hard to know. I think there have been some who have gone months abstaining, and still had symptoms (albeit lighter).