How long is too long for a couple to live together rather than marry?

I know many people say “It’s only a piece of paper” but in NY that paper means a lot.
Some background: Recently a friend of mine died, suddenly, at age 57. “John” had been living with “Mary” for 25 years. They both had good jobs and both wanted no children so neither one felt the need to get “the piece of paper”. They each had their own bank accounts and split expenses right up the middle. About 10 years ago he bought a lake front cottage for them to enjoy on long weekends. They both worked on it and made it into a nice vacation destination.
The problem: John never made a will. And NY does not have common-law rules. They did not have the “piece of paper” so Mary is not considered his spouse. With no will, all individually owned property and bank accounts goes to his estate and ultimately to his only surviving parent, his mother! Since he never filled out the beneficiary box on his retirement account his mother gets that, too.
Fortunately John and Mary owned their home jointly so at least that goes to Mary but the cottage is gone.
Hindsight is 20–20. Had they decided to live together for 3–5 years before marriage Mary would have been left with something. Now she’s left with a double tragedy.

Are any couples here living together for a long time? Does your state have common law rules? Do you have wills and have you named beneficiaries? Or are you just ignoring the whole mess and figure it will all magically work out?