I can only speak for myself, but the cut off for me was his book, 'Where We Are Going', or whatever it was. I read the whole thing in basically one setting and threw it into the trash immediately afterward. And it takes a lot for me to throw a book away. I think I had already stopped attending Pastors' School, but I'm sure I bought nothing else of his afterwards. It was all about the same time that a staff member told me privately about his foul mouth, and I washed my hands of him.
There were some of his earlier books that I never bought, such as his book on depression and on temptation. Others of his books I found very helpful in spots, including some of his book on marriage, his book on Proverbs, and especially his book on prayer. I think that was his best book. But even in those books the margins of mine are all scrawled up with 'nonsense' and 'oh brother' in whole sections and chapters.
Perhaps it was as he changed I was changing at the same time, wanting something deeper and with much more substance, with much more adherence to the Word of God and much less personal philosophy. I was also getting really nauseated with the whole FBCH system, and how it was expressed in teaching, magazines, books, etc. But I can filter that, if what I think I'm reading is worth it.
That's just me. Every guy has to answer for himself where that line is in relation to what he reads and why, and I don't think there is any specific right or wrong answer. It is sad to read JS' books after the disaster b/c certain things he says here and there are just heartbreaking, in relation to the wretched decisions he later made, and the price he is paying.
I don't quote him, though. Even I'm not that stupid.