I'll say this, purely from a reasoning standpoint and not from a research stand point. With my wife, we dated for a year, cohabitated for a year, and were engaged for a year before we were married. This made sense to me because you get to experience all the holidays at every point in your life, and it let's you see each other how you exist throughout different points in the year. If you need the AC cranked in the summer, and your parent can't stand that, or if you want to bake all winter and stay inside while your partner wants to go out all the time, you aren't able to discover that without cohabitating for at least 1 year.

Here's the fun answer. Never move in. Have your own place where you can pursue your hobbies and they have theirs. Date for years and years, stress free. No fights about animals, housework.

Bonus: it makes the time you spend around that person genuinely fun, planned, and enjoyable.

I hate that the system generally forces people live together because it's otherwise too damn expensive. I feel like if it wasn't, probably more people would choose to live this way.

You're not going to get a useful number for this. There's simply too much variability between cultures, communities, and individuals for ant number to make sense. This relies in factors including emotional maturity, work loads, financial situations, friends/family/pets/children, leases, etc...

"Waiting until marriage" is usually under the assumption you will combine finances and have kids and take on debt (house ig) immediately while learning how to live with eachother. So several peak stressors at once. Maybe your citations are hoping the couple gets trauma bonded?

Also I've personally never known anyone who married before spending multiple years cohabitating.

My now wife movies in with me pretty quickly, maybe like 8 months after we started dating.

We spent a lot of time together as it was, but Covid came and her sister was doing her residency.

I was happy to have her move in as it would limit our exposure and we could still see each other.

Shortly after that, she moved in with her parents to look after them for a few months and we just did a long distance thing as the city went on lockdown and they lived outside the city.

After about 6 months she moved in. We ended up getting married like 2 years or so later.

We have have been married for a year this October and things are great. I love living with my wife and I always have.

Of course there were times that were hard as we adapted to so emotional each others habits and stuff. One example, is that I’m a super light sleeper so she had to adapt to be extra quiet while I’m sleeping.

She grew up and lived next to an airport most of her life, so her entire family are heavy sleepers.