I bought one of the biggest Toro's they had, traded my 8hp in for the bigger one, the old one was about 15 years old. I think the new one is equivalent to a 10hp. I got it used, only two years old. Dying to try it on a 20incher.
Hasn't happened in 26 years yet so I assume it won't. I had a new roof installed last year and unbeknown to me they ripped up the gutter guards with the old roof and threw them into the dumpster. Back a few months when we got the heavy rains what your describing is exactly what happened. Even got water into my basement for the first time. I cleaned the gutters and installed the guards and everything's been hunky dory since.