Good discussion here.
Thanks to Jenn and Jenni and a few others here, I do use the "30 wears" test at point of purchase. Not so much as a budgeting tool but more in consideration of the environment. But I use it rather loosely, more as a reminder to think about the impact of my decisions and ask myself whether this is a valuable purchase or whether I'm shopping for some other reason.
And if something isn't working for me, I don't force myself to wear it 30 times. I let it go.
Contrariwise, I also wear many of my clothing items many many more than 30 times. That's pretty much the definition of a workhorse.
Those with very small wardrobes won't necessarily get 30 wears from each item -- it all depends on the amount of "wardrobe churn" they tolerate. And sometimes things wear out faster when your wardrobe is small -- maybe even before 30 wears.
If your style is "classic with a twist" (or something like that) you can probably get 30 wears from a lot of items just by holding onto them for a long time -- even if you have a huge wardrobe. But people with a trendier style will want to wear their clothing a lot in the first year or two and then pass it along. It's all so personal.