Can an average human suck their thumb forever none stop?

Though there are cases of severe adult thumb sucking (usually found in prisons, and places that care for mentally handicapped people) it can't be done non-stop because the individual uses their mouth for eating, etc. There was at least one case where a mentally handicapped woman, age 65, continuously sucked her thumb to the point of actually causing severe skin damage. She was forced to cease in order to allow her thumb to heal. This was achieved by substituting a pacifier, but she eventually started sucking her thumb again.