If you were only interested in an 11 year gap, then I can't see why anyone would actually purchase an annuity. I'm planning on having one in place to bridge to age 70 for SS.
I'm a bit confused - you say you are going to get an SPIA as "gap insurance" for SS at age 70. Yet that is the reason I got it? What's the difference?
That was my primary reason for the SPIA, however since I know (and planned) that the SPIA would have less purchasing period in the remaining guarantee period (for us, from age 71 to age 87) we were just looking at it as "extra fun income", not necessarily required (easy enough to plug into FIRECalc as a reduction in income at a specified plan - and we're still at a 100% sucess rate even without the annuity income after age 70).
- Ron