its a matter of personal taste, by all means sample a bottle as soon as you want to, i think i prefer my beer more mature than some as i will gladly let a brew sit for a couple of months.
generally speaking beers with lighter malt bills tend to mature quicker, and beers brewed with dry hop additions for huge aroma effects tend to be drunk green to get the most aroma in the pint.
as a rule of thumb if you dont think a brew is at its best when you sample it let it sit a few more weeks before cracking another sample..