Is There a "Right" Age for Marriage?
"It's Never Wise to Set Arbitrary Age Limits"
If 18-year-olds have proven themselves willing and able to implement interpersonal skills and neither suffer from or wish to inflict upon the other any of the three "Big A's"---Adultery, Addiction, or Abuse---then sure; many great loves began well-before 18-years-old, and it's never wise to set arbitrary age limits upon ANYthing, for all mature at different rates.
Most relationships fail due to unspoken/unexpressed expectations of the other; "the bloom is off the rose" when what was EXPECTED is not what is REALITY, and the honeymoon period ends.
Meet the community member Hatman here