The older I get and the more that I have (to lose in divorce), the more I seek sanity, so testing for it early is crucial.
You don't get many workarounds in life with a sanity test failure, just pain and expenses.
Personally, living single isn't the best way to go through life, but I think it's better to be alone and looking for a right one than being with the wrong one. Less damage all around that way.
Marrying well is its own reward.
One thing that really helped me (relationship-wise) was the old “Divorce Court” series (mid Eighties). Watched every episode I could. It was all supposedly based on true cases and taught me a lot about dysfunctional women & relationships. I also had a few experiences where I dated good looking women who weren’t emotionally stable—after a while, they seemed downright ugly. In contrast, average women who were stable actually looked better over time.
But, I definitely agree: Sanity is the most important attribute in a mate.