At what age does this begin to thicken and when it happens is it quickly like within a month or 2 or slaowly like over a period of 9 to 12 months? I ask because it seems like the neck of my male is increasing in girth slowly over months, but it seems to be consistantly enlargening. My female is not doing this and I do not know how old they are. They are supposedly abot 5 or 6 years old. I'm wondering if one is older than the other, or if both are older than I was told upon purchase.

