Does "The first year of marriage is the hardest" rule apply in this situation?

I’ve heard the saying “The first year of marriage is the hardest” many times and I can understand why that would be. But if a couple has been living together for say 5 years or more, sharing bills and household responsibilities and have their roles in each others lives and home established before they were married, would the saying still be “correct”? Or would things still be the same as they were before the wedding just now they are bound in name and by law?

Please No Rude, Twisted,Degrading, ect. Comments.