I've heard it said that fountain pen nibs "wear in" to the angle you use to write with them (at least in older, softer nibs), and that you should avoid loaning out your pens because the person you give it to will write at another angle and give it a second wear point, ruining the nib. Is this true? Are you able to tell by looking at a nib where the wear point is? If this is true, how common is this phenomenon? (Should I loan my pens out or not?)
I collect pens from the early-mid 20th century, so should I be concerned with this?