I asked this question recently, unfortunately it did not get me closer to an actionable answer. Of course clothes get damaged and stuff is in the lint drawer, but it is a huge difference between losing the longevity by a 1% and 30%. Any actual research would be tremendously helpful.
This isn’t scientific, but was recently listening to a podcast where they interviewed someone (18 minutes in) who does laundry for the Nets basketball team, and he said that the dryer basically bakes in any sweat or blood or stains which don’t get washed off before. I’m not sure how this affects longevity of the fabric, but from a usability standpoint, if your clothes are permanently stained, you probably will stop wearing them.