LDR couples should at least spend a year together where they stay with each other for a couple of weeks or more to see how the other lives.

I mean even this isn't a lot overall. The honeymoon period in "normal" relationships lasts around 1-2 years. In long distance, it's often longer. Then add the factor of age.... as a teenager and person in your early 20s, you haven't got much dating experience and don't really know what to look out for in terms of possible compatibility issues.

Another option many people forget: instead of moving in straight away, have the other person move to the area, but live in a flatshare. That way you can date "properly" and figure out if it might work before getting on a lease together.