I don't think there is anything necessarily bad about getting into LTR's early. That's what I did, and it was good experience. Though, I wish I had done that game-aware, with resources such as this to help me figure things out.
I think the hazard is that a young man might take the relationship seriously - and have it effect his school, career, or hold him back mentally.
So, I think it's best that younger men don't take their early relationships very seriously at all.
This. I count myself lucky to have had an extremely educational 3 year LTR before the age of 30. Some marriages last less time than that. Truth is, you learn a lot more about yourself in an LTR, than the opposite. The worst you have to contend with when spinning flakes is flakiness and escalation.
Much easier to develop a thick skin against rejection and next plates that misbehave than to manage an LTR with a hot, attractive women, where you pretty much have to have iron balls 24/7. To keep the best women in a perpetual state of attraction you have to BE game.
Young guys (or men in general) shouldn't be seeking out LTRs, but if a hottie keeps you interested and wants commitment, then if it's something you want go for it, as long as it something you benefit from.
LTRs are great, provided you don't compromise yourself or your long term goals. Don't let any woman keep you from seeing the bigger picture.