My beardies' stats are as follows:
Gryphon:
Age: 4 years ( on May 15th!!!

)
Sex: Male
Length: 23" STL
Weight: 710 grams
Boggart:
Age: 3 1/2 years
Sex: Male
Length: 19" STL
Weight: 390 grams
Kirin:
Age: 11 months
Sex: Male
Length: 16"
Weight: 210 grams
All three have identical housing and nutrition.
Gryphon was purchased from Georgia Bearded Dragons (S: Scrappy D: Cleopatra) in 2009 at 2 1/2 months.
Boggart was rescued at 4 months and was in bad shape but has overcome previous malnutrition and questionable (at best) husbandry quite nicely and has grown up to be a completely healthy adult.
Kirin was rescued at 2
days and has
never been without optimal husbandry and nutrition and yet is very small, but a very healthy boy. Some size aspects can be linked to environment, but each dragon is unique and has his/her own set of genetics that predetermine his/her size, regardless of husbandry and nutrition (aka baby Kirin).