"How can you be sure SS will be there?"

I had the same thought. Plan was to wait till 70, but ended up taking it at FRA. Ran the numbers a dozen different ways thru a SS, and determined it doesn't really matter too much. I definitely see Intercst's point on delaying, and I definitely understand the worry about the solvency of the "Fund". It's been quite the inflation runup, and if the SS payout continues, then the COLA is a helluva deal. My pension offers no COLA, but the monthly check helps me be a better stock investor, and it's the same with the monthly SS.

So barring any hyper-inflation scenario in our future, you'll be OK no matter if you take at FRA or delay till 70. I just can't totally discount a hyper-inflation future. Last I read, national debt is increasing by $1 Trillion every 70 days under Trump, and it's probably worse than that, I do not trust any of the numbers this admin puts out. So SS cuts and inflation are valid concerns for all of us retirees, imo anyways.