No, we don’t need two dozen Presidential candidates a year and a half before the actual election. But we really have no choice in the matter:
The problem with trying to limit the length of presidential (or any) electoral campaigns is that we have that pesky Constitution, in the form of the First Amendment.
If it’s (say) a week before Thanksgiving and someone says, “When I’m president, I will …”, telling someone that “You’re not allowed to say that yet” would result in you getting your pee-pee severely whacked by the courts, and deservedly so.
The Brits get away with their 60-day election campaigns by simply banning election speeches and so on before the start date. Try doing that in the U.S. of A., and a shit-storm will ensue.
It might even be a bigger storm than the actual campaign, which for 2020 promises to leave no fan untouched by fecal matter,