Get LTRs when you want to start thinking about building towards kids and either marriage or cohabitation. Basically age 14-25 -> fuck girls for fun, learn how to get laid at parties, by social situations, by clubs, through your hobbies, etc. Learn to have low-key FWBs, bootycalls, and other forms of plates. This gives you a shit ton of experience on how to read and deal with women.
This also keeps your mind clear and you focus your youth on building up your SMV (career + physique + game/social skills). You are too young to have reached the point where you can leverage your SMV/RMV into getting a high value, decent woman yet.
But you reach a point where you want to build a legacy - kids, family, etc. For that you need a woman, and you use what you learned from years of plating to screen and lead the best woman you can.
This is why a guy needs to be the cock on the carousel for a while; he will make a shitty decision 100% of the time if he has insufficient experience and points of comparison, I guarantee it. You are the man, so you are responsible for providing leadership and direction; you take the best girl you can get, and through positive dominance, leading by example, dread game, and sex, you turn her into a someone better than her programming.
See, I do believe women play an important role in raising kids. They have their strengths too, and as a guy who does want kids someday and want my kids to have the proven benefits of a healthy family unit, LTRs will be essential.
If you do not have a purpose for the LTR, how can you lead? How can she understand the vision and purpose behind the LTR if you have none? Women submit only to be a part of something greater than themselves - as much shit as we talk, women will sacrifice literally anything and do anything for a higher value guy. If you are cleanly head and shoulders her superior and she knows it goddamn well, she'll be a damn good LTR (at least, until it gets in her head she can do better).
Marriage is basically saying "I bet half my shit that I will always be higher SMV than you."
Which as a guy, you damn well should be. Her SMV will decline, yours will rise if you just stay sharp, improve yourself, and dominate the relationship. You'll get a great partner some of the time at least if you take good base material (low n-count girl with passions in life and feminine behavior) and mold her and lead her to becomming a good LTR. You just have no fuck-up allowance.
Think about the best gladiator in ancient rome. He can fight 1000 duels and crush his opponents, but he fucks up and slips up some sand, and some newcomer kills him, then he's forgotten and everyone hails the new kid on the block as the GOAT gladiator for killing him. This forces the best gladiator to always stay sharp and always train to be head and shoulders above his peers.
This added pressure... it sounds terrible. But if you accept it and let it shape your ambition and urgency to achieve things in life, it can be a fantastic thing. It can keep you from getting fat and saggy in your 30s, it can keep you from getting complacent, settling down with a mid-tier 9-to-5, and drowning yourself in gaming. Having this additional demand placed upon you will either destroy you or make you better.