Queen Elizabeth II is 86 and showing scant sign of calling it a day. Spain's Juan Carlos, currently enduring the toughest of times as his debt-ridden country goes through hell, clings on at 75. Albert II of Belgium, sometimes seen as his country's sole national figure as Flemish separatism moves into the political mainstream from the fringe, still occupies the throne at 78. Margrethe II of Denmark has just chalked up 41 years as queen ahead of her 73rd birthday in April. King Carl-Gustaf of Sweden, embarrassed by a recent stream of philandering allegations and kiss-and-tell revelations, is a relatively sprightly 66.
This week, the Dutch bucked the trend. Just ahead of her 75th birthday on Thursday, Queen Beatrix announced she was to become a princess instead, abdicating in favour of her eldest son Willem-Alexander who, at 45, is to be inaugurated at the end of April as the first male in the top job since 1890.
More than 7 million people, almost half the population, watched Beatrix's three-minute abdication statement on television on Monday. The general verdict was that the manner of her leaving was as gracious, as firm and as decent as her 33-year reign.
"I've been asked this for 10 years - when will she go," said Reinildis van Ditzhuyzen, chronicler of the house of Orange. "And the answer was always, I don't know. But she has chosen the right time, as she turns 75 and with the Dutch kingdom marking 200 years."
Abdication is an extremely rare event among the monarchs of Europe, albeit not for the Dutch. Queens Juliana and Wilhelmina, Beatrix's mother and grandmother, both made way for their daughters.
Elsewhere, it seems to be unthinkable. An abdication in the house of Windsor might trigger a crisis in the UK, at least it did the last time it happened in 1936. It has never occurred in Sweden's 195-year-old monarchy, although the opinion polls show a majority wishing King Carl-Gustaf would go and make way for his more popular daughter, Crown Princess Victoria.
King Juan Carlos has just survived the worst year of his reign. For the first time since his starring role in stabilising Spain's post-fascist democracy in 1975 and warding off an abortive military putsch in 1981, he has become a laughing stock.
Allegations of sleaze and revelations of family dysfunctionality are weighing heavily on the royals in Belgium, with Albert this week forced to issue a highly unusual statement confessing he had been "humbled" by tales of financial impropriety involving the 84-year-old dowager Queen Fabiola, the widow of Albert's late brother and predecessor on the throne.
And the ageing monarchs of Britain, Spain, and Belgium may even be witnessing their realms' end to an extent, owing to secessionist pressures in Scotland, Catalonia, and Flanders, the latter two being strongly republican.
In this context, Queen Beatrix might be seen to have cannily set the right example, injecting greater dynamism into the dynasty by handing over to a younger generation.
"The Dutch have difficulty accepting all the heritage stuff. You really have to work hard at being king or queen. It's very much seen as a career," said Daniela Hooghiemstra, a historian of the house of Orange. "So it's better if you're not too old. If you're 80 years old, it's hard to bring in new ideas. What Beatrix has done means that the monarchy will keep up with modern times."
If queens Elizabeth and Beatrix have had a good year, Europe's ruling males are faring a lot less well. This week Juan Carlos's son-in-law was ordered to stump up €8 million bail or be imprisoned in a embezzlement investigation.
The sleaze claims come as Spain struggles to weather a devastating financial and economic crisis with unemployment nudging 30%. In the middle of the crisis last year, Juan Carlos initially sought to hush up an all-expenses-paid big safari excursion to Botswana. The image of the king shooting elephants in Africa while Spaniards lost their jobs and got turfed out of their homes was damaging. For the first time in his 37-year reign, the king is now the butt of satire and contempt on stage and in the newspapers in Madrid.
His son Felipe appears eager and willing to take over the throne, but the response to events in The Hague this week was blunt: the king is not abdicating.
Events in Brussels bear an uncanny resemblance to those in Madrid. Albert II might be regularly credited as the sole national figure holding Belgium together. He might end up, though, as the last king of Belgium. At the new year he denounced political "populism", comparing it to 1930s-style fascism, seen as a dig at the man making the political weather in Belgium, Bart De Wever, the leader of the separatist New Flemish Alliance, mayor of Antwerp, and a republican.
Unlike Scotland or Catalonia, Flanders is the bigger part of Belgium. Flemish independence would mean the end of Belgium.
After public outrage at the shenanigans of Queen Fabiola - alleged to have created a family foundation to funnel taxpayers money to her children and avoid death duties - the government has just cut her allowances by €500,000 a year, or around one third. "Recent events have pained me and dealt a lesson in humility," King Albert declared on Tuesday.
"He knows how fragile is the institution he represents," said Le Soir, the main French-language newspaper.
In Sweden, Carl-Gustaf has also become the target of smirks and giggles after a pop-singer, Camille Henemark, published a book going into gory detail about her alleged affair with the king in the 1990s.
At 66, Carl-Gustaf is considerably younger than the other crowned heads, but nonetheless of an age when most people retire. An opinion poll showed 60% of Swedes thought he should quit. The Swedish press is full of stories about his drinking habits and visits to strip clubs. The royal reputation has suffered badly, with Swedish women in particular turning against him.
"The thing about monarchies is that they flourish as long as they are doing their jobs well," said Van Ditzhuyzen. "If they behave badly, the support crumbles. Monarchies have enormous elasticity and can often recover. But there comes a breaking point. And in the old days the kings or queens would die at 40 or 50 or 60. Nowadays they can go until they are 90."