Senator
Thinks s/he gets paid by the post
The downside to no kids and not married could be a very bleak and lonely existence late in life. Especially true for females as life expectancy is longer.
I have lived with the same DGF for 24+ years, no different than a wife, but all finances are separate. It helps. Marriage is obsolete now anyway. No financial arguments, save what you want/can. Get the combined living savings. We are both in the LBYM camp, and saved quite a bit. There will never be a FIRE abort due to a divorce.
You also get tax savings, and one person can be low income for HSA subsidies, EITC and other programs, letting their retirement accounts grow, while the other makes the money. Get married at a late age for SSA survivor benefits, just before you can actually get them.
No kids. When I get older, I can hire someone to come and visit me. Likely the kids will be too busy, and working, or living in another state, to really care to visit too often.
And the [-]strippers [/-]people I hire to visit me when I am lonely won't be old folks like my kids would have been...
Kids or no kids, wife or no wife, LBYM is crucial. Max out all savings you can. 401K, HSA, IRA, etc.
Great job to the OP, they are well on their way.