Fixed index annuity with 10-12yrs deferred

I'm 52 and looking into a fixed index annuity with a long deferral, roughly 10 to 12 years before I'd start taking income. Still working, and don't need this money for a while, so a longer runway seems reasonable if the growth potential is actually there.

From what I've read on [Annuity.org](http://Annuity.org), fixed index annuities can have strong long-term growth potential because your returns are tied to a market index while your principal stays protected on the downside. That combo is what pulled me toward the idea in the first place.

As a rough example, I'm thinking about putting in around $250k now and letting it sit for 12 years before switching over to lifetime income. On paper the numbers look pretty good but I know sales illustrations and actual performance are two different things.

For anyone who's held a fixed index annuity through a long deferral, what were the downsides you didn't fully see coming?