What makes a white T-shirt worth keeping?

The white T-shirt I reach for most is no longer perfectly white. The collar still sits right and the fabric has become softer without losing its shape. 一直在想，“基础款”里最值得留下来的细节是什么。你会先看领口、布重、袖长，还是洗过十次以后的样子？想听实际穿着经验，不需要列购物清单。