Honestly, stocks should trade for three hours a day. 24/7 trading sounds like a win for exchange operators and a loss for anyone else.
If that were true then nobody would show up to trade during the extended hours and therefore absolutely nothing will change.
And even that seems kind of generous to me. I see absolutely zero value in stock trading continuously for any length of time. Businesses don't make purchasing or investment decisions in that time span, nothing of significant value can even be created or sold or shipped in those time spans.