I'm not the OP, but started seeing DH when we were 19 and are married with a son in out mid-40s -- in answer the questions about boredom. I've genuinely never been bored by him, but then, neither of us ever saw a committed relationship as a reason to 'settle down' or limit ourselves.
I think the thing about getting together so young is that, inevitably, you change, and the relationship is either flexible enough to adapt to that, or it ends. Having said that, though, we're both restless, easily bored people, who didn't ever plan lives of school, university, job, mortgage, marriage, children -- we've moved around the world a lot, done lots of different things, sometimes in different countries, had our only child at 40, and the seven years we've spent in rural England (not from the UK) is the longest we've spent anywhere since we met.
He's lovely, and I'm astonished I made such a good decision in my teens.