My parents bought (or were sold) one in September 1997 when my Dad was 61 and my Mom was 58. It was purchased through a life insurance agent at a well-known and generally well-regarded insurance company.
My parent's opinion (which I think probably mirrored the agent's sales pitch) was that they were concerned about estate taxes, and they didn't want us children to have to sell assets to pay estate taxes because we might have to sell at a bad time.
My Mom passed away in 2016. My Dad is still alive and in average health at age 85.
The insurance agent originally said that the policy would probably be paid-up in about 10 to 12 years. I don't think it ended up being paid-up that quickly, and for whatever reason my parents decided to continue paying the premium anyway until last year. It does appear to be paid up now in year 24/25.
As an investment, it seems to have approximately returned about as well as a bond fund - about 4% a year. Which is fine with my Dad.
Based on how the life insurance policies worked when my Mom passed away, it does appear that it would function as intended - we got tax-free cash when she passed away that could be used for whatever, including estate taxes.
My parents did end up putting the second-to-die policy into an ILIT, which seems to be functioning as expected and is a helpful thing to do. Since the policy is not owned by the decedent, the proceeds are not counted towards the estate value. There is some paperwork to set one up and transfer the policies, and then annually my parents gifted to the ILIT the premium, and my sister the trustee sent out Crummey letters, but all in all not too much hassle.
The possibility of estate taxes being incurred has varied over the past 25 years as the limits have changed and my parents' assets have changed With better planning I think they could have probably been completely avoided - we did not elect DSUEA when my Mom died, which it seems now would have been helpful. As it is, it's something to manage but the amount of estate tax due will very likely not approach the amount of life insurance in place.
After watching the policy underperform the insurance representatives projections over the past 25 years, and watching the performance of the stock market over those same 25 years, and watching the estate tax limits get raised over a similar period of time, I personally think that my kids will end up better off if I do not purchase any whole life insurance. When I die, if my estate owes taxes, they can just sell something to pay the taxes. Even if the market is in a temporary funk at that point, I still think they'll be better off. So I own zero life insurance at this point.
I would add, though, that if your AA includes a sizeable portion of bonds, you could consider the second-to-die policy as a bond equivalent. In that way of looking at things, setting up an ILIT with a second-to-die policy (or any whole life policy) seems like a tax efficient way to move money out of your estate.