If we make adolescence longer legally will this help and increase life?

Studies have shown the the "Adolescent" brain continues to develop into the mid 20's but I dont think a person is really an adult until the age of 30 cause certain stuff I dont believe a person under 30 should be doing like drinking,voting,having or signing a contract.The only reason they let an 18 year old fight in war is because of their lack of maturity and they are impressionable.The government is stupid for giving 18 year olds adult rights maybe in the past but now we know that the brain "Frontal lobe" developes between 25-30 and I also think education should be extended.