Halley's Comet can be seen from the earth every 75 years or so.
And the Curse of the Bambino was blamed by many followers of the Boston Red Sox for their 86-year wait for a win in baseball's world series.
So, in truth, the patience of Queen of the South supporters in waiting for a Scottish Cup semi-final is small fry in comparison.
After all, it is a mere 58 years since they last made it to the final four of that particular competition.
Fans joke that since then they have followed them through "thin and thinner".
Now, on Saturday afternoon, Aberdeen stand between them and the final.
For most Queens followers it will be a once-in-a-lifetime experience.
QUEEN OF THE SOUTH FACTFILE
However, a tiny handful have seen it all before - even if they were a lot more youthful the last time it occurred.
Former railwayman Willie Gordon was working on the morning of the 1950 semi-final with Rangers and then travelled by train to the cup clash.
"That was one of the best days in my life," he recalled.
"It was one of the best cup ties I think that Dumfries supporters had ever seen.
"Queens matched Rangers player for player and they were leading one nothing up until they gave a rather freakish goal away."
That goal is the stuff of legend at Palmerston Park.
From a corner kick goalkeeper Roy Henderson famously shouted on Dougie Sharpe to leave the ball to him.
"Dougie let it come and it flew into the net and that was it, they equalised late in the game," said Mr Gordon.
Queens lost the replay but that trip to Hampden still has a lot of fond memories.
"It was the best atmosphere I have ever savoured in football," said Mr Gordon.
"We stood among the Rangers supporters, there was no segregation and there was no trouble whatsoever.
"That was our year to win the cup, we would have beaten East Fife in the final."
Club chairman David Rae was also a Queens fan in the 1950s, although he missed that particular game.
He said it would "mean the world" if his team could win the match this time around.
The chairman knows that the supporters heading up the M74 feel exactly the same.
He believes the omens may be good for Queen of the South to overcome Aberdeen on Saturday afternoon.
"Some people talk about a lucky 13 or unlucky 13," he said.
"I am the 13th chairman of Queen of the South Football Club since the last time we were in the Scottish Cup semi-final away back on 1 April 1950.
"So maybe I am going to be the lucky 13th!"
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