WordNet sense 1 (having a full and pleasing flavor through proper aging):

mellow

WordNet sense 2 (at the highest point of development especially in judgment or knowledge):

ripe

WordNet sense 3 (being at the best stage of development):

prime

WordNet sense 4 (fully ripe; at the height of bloom):

full-blown, matured

WordNet sense 5 ((of animals) fully developed):

full-grown, grown

WordNet sense 6 ((of birds) having developed feathers or plumage; often used in combination):

fledged

WordNet sense 7 (being changed over time so as to be e.g. stronger or more complete or more useful):

developed

WordNet sense 8 (develop and reach maturity; undergo maturation):

grow, maturate

WordNet sense 9 (cause to ripen or develop fully):

ripen

WordNet sense 10 (grow old or older):

age, senesce, get on

WordNet sense 11 (cause to ripen and discharge pus):

suppurate