Great post by Orionpilot. There is no best answer for everyone, but here's why I don't agree with Catfish:
Most financial planners I have met over the years say to plan on $40k a year per $1M invested. Reasons vary, but a couple are: inflation (your $ will buy less later than it will today), tax (cap. gains).
Whole life is the worst possible investment. Ask ANY financial planner who doesn't sell it. You will benefit more from nearly any other form of investment. As for the best type of death insurance (that's what it really is), term is very hard to beat.
Once receiving SBP payments after your heart quits, your spouse will get a small COLA raise most every year. Her SBP payments drop to 35% when social security kicks in, but her gross monthly income will not go down. If she lives to 102, they just keep on paying and giving COLA raises.
Other than whole life policies (see above why to avoid these), I don't know of an equivalent life insurance plan - (fixed-rate, lifetime monthly payment to beneficiary, annual increases).
SBP alone is a joke, unless you plan to live in a single-wide trailer (not a bad idea, it would sure simplify planning). For me, the best plan was to take SBP, and pick up a 10-year level term policy which I hope I am healthy enough and finanicially sound enough to renew 10 years from now. I also took the max insurance available thru my employer - best rates around.
What happens if you can't renew your level term policy in 10 or 20 years because you get sick? You could have a decreasing term policy which fizzles out when you are 70 years old, or you could have regular term, which costs more and more to maintain as you age, until you are priced out of it. Your spouses need for monthly income SHOULD decrease as she ages (kids out of the house, mortgage paid off, boat paid off, etc.).
I am not confident that if I die at 71 and my wife lives to 95, that any insurance I have now will still be in effect then. But SBP will. A Roth IRA and a 401k can do more than any of these others. That combined with long term care insurance when we get a bit older, should cover her and leave a nice inheritance for the kids.
SBP is a good pre-tax way to have some permanent peace of mind. If you die, it will come...........forever (until your spouse dies). It isn't the big "ka-ching!," but it keeps the lights and the heat turned on. She can get the big money from your other insurance and investments, then struggle with investing those properly, paying a broker or financial manager, paying a tax atty or accountant, and paying excessive taxes. Meanwhile, that little SBP check just keeps on coming - month after month.
After all that, if you can find another combination of insurance and investments that are as reliable for such a long time, and both you and your spouse are comfortable with all the possible payment scenarios, go with your plan - with or without SBP.