Imagine if the day after Halloween, trick-or-treaters decided to return for a second dose of sugary delights and egg-related threats? Or, if after every Valentine's Day, hopeless romantics expected their loved ones to whisper sweet nothings for a further 25 hours. Madness, we'd say. Once is enough.
And yet Orthodox Jews regularly enact a version of Groundhog Day. "For seven days you shall eat unleavened bread," Exodus says, yet outside Israel we deprive ourselves of leavened goodness for a drawn-out eight.
In the days of the Sanhedrin, a chain of bonfires would be lit at each new moon to alert Jews in far-flung places to when the chagim would fall. It was hardly foolproof, and so it became that diaspora communities observed two days where their brethren in the land (and now state) of Israel marked one.
While we no longer need this margin of error, we continue to endure second Seders and double our cheesecake-consumption. All because of minhag avoteinu b'yadeinu (this was the custom of our forefathers), so it would be wrong to change course. Reform Judaism, by contrast, goes by the Torah.
Perhaps some people - rabbis, I imagine - enjoy two consecutive days of Yom Tov, even if there is little difference between proceedings. It can be a godsend for split families.
Personally, by the end of the first day, I've had enough. But that's not the point. What matters is what it means in the longer-term.
For mainstream diaspora Jews, life is a balancing act between the demands of religion and those of wider society. That's true of keeping kosher despite the availability of all kinds of food, or of walking home after Friday-night dinner when the tube is running anyway and you have a pre-paid Oyster card. But there are modern solutions, like eruvs, that make life easier for the modern Jew. Not ways around the rules, but ways to make the rules co-exist with reality.
As a pupil at a non-Jewish school, I was one of a small minority who took off the full run of the shalosh regalim, playing catch-up for the first half-term. At university, I watched friends stay with chaplains the night before finals because exams clashed with Shavuot.
Now in my 20s, I look at friends who did those things - who in their adolescence fell under the category of modern Orthodox - and many no longer do them.
For some, steering away from their religious upbringing is a choice; for others, sadly, it is done out of necessity. In a tough job market, employees know they need the edge, and that doesn't include several weeks of disruption every year for festivals the majority of non-Jews have never heard of.
For some, if you can't take the full set of days off, why bother taking any? "I'll do it when I'm older," friends say. But will they? Or will they get used to a life where the traditions of their childhood are marginalised.
Five fewer second days every year wouldn't make it easy, just easier. The strictly Orthodox will always find a way; the extra day is irrelevant for twice-a-year shul-goers. But what of the middle ground, the people who grew up joining in the shul Simchat Torah party? Where will these children come from in another generation, if their parents find Judaism so reluctant to adapt.
Jewish life is about far more than religious observance. But, to misquote Ethics of the Fathers, we need to build a fence around our future. Just because generations of Jews have done it, doesn't mean Jews should do it for generations to come. Many aspects of Orthodox Judaism could do with modernisation, and none can be solved by a rabbi waving a magic wand. But second day Yom Tov is a rabbinic invention, that was borne out of need.
The discrepancy with Israel is illogical and outdated. If only our rabbis today could find the courage to do something about it.