How to age bristlenose plecos

[MiniMedic]

Hello

I was wondering if it was possible estimate the age of bristlenose pleco. Mine is about 1.5 in. in length. I suppose size is relative to environmental conditions and diet so I was wondering if there are any other signs of age, or perhaps of sexual maturity.
The store employee mentioned it taking roughly 2 years for it to reach full size. What are your experiences with bristlenose pleco growth?

 

[dalto]

My experience is that they grow fairly fast to the 3.5-4" range than they slow down a bit.

An 1.5" fish is quite young.