Subject: Re: Portfolio123
P123 usually considers 10 years to be near optimum.
Seemed odd - here, it's always been "the longer the better" which makes intuitive sense.

10 years back is 2016. That period has been mostly a bull market without ANY bear market. Just a couple of shortish corrections.

Any backtest which doesn't include at least the 2008/2009 bear market will be telling you sweet nothings.