The specific length of a persons beard (or hair) which makes them reluctant to cut it off as they have never experienced such a length. Or, because they feel that their beard has become important to them, like it's their child.
Note: Often occurs in teenagers and young adults who are notoriously shit at growing beards and tend to cling desperately to any facial hair they can muster.
Ben: Man, your beard is disgusting!
Pete: Yeah I know, but it's reached reluctance length so I can't cut it off yet.