On average, the Kotn shirts I have owned have lasted about 2-3 cold-washes before they fall apart or shrink profusely.
Do not recommend this brand.
I have contacted their CSR regarding my concerns. They provided me with some credit, which I used, and the same quality issues plagued my next order. I followed up with the CSR who again offered credit, and I am pretty sure that credit is just rotting in my inbox. I have no intentions of wasting more time with their items.
A few years ago I bought a pullover from them that had some of the sloppiest stitching I have ever seen, worse than anything you'd find at fast fashion places even. They offered to send me a new one, or to give me a refund. I took the refund.