What happens when another 1999 happens with three straight years of 20-30% declines? Or a 2008 where there's a nearly 40% decline? It takes several years of double digit gains to recover from these declines, and both of those happened within a decade (and we are not even a decade out from 2008).

Point is, investing v. paying off debt is not a simple matter of average expected growth compared to interest paid on loans. Investments often lose large portions of their value in the short-term while paying off debt is always a guaranteed return. So, for short loans (<15 years), it's probably not wise to use average expected return, instead use a wide range of +15%pa and -30%pa.

I'd argue the fact that you've beaten the average expected yearly return for so long suggests that a correction is imminent and paying off debt has a better expected return than investing. This goes doubly because so many people have forgotten the lessons taught by past recessions and believe that 10%+ annual returns are the norm.