When you think the inner-child hiding inside you has given up, it's time to try something different.
Cruises don't usually fall into that category. They can be terribly samey and predictable. And, let's be honest, everybody is doing them.
But boarding an ocean-going liner in the heart of London and then gliding out under Tower Bridge, which parts especially for you, before sailing down the Thames into a glorious red dusk, is definitely something different.
Before setting sail, we had gathered in the observatory lounge of the slim, sleek and effortlessly pretty 'Le Boréal', each of us clutching a glass of champagne to witness the moment and hear the horn sound the traditional farewell.
On this eight-night cruise - set to take Le Boréal to Belgium, then back up the North Sea to Tyneside and Scotland, before finally resting in Norway - no other moment could compete with this.
Ponant, a Breton cruise line with a fleet of several small ships, including what it calls super-yachts, sees itself as an alternative to the Royal Caribbean, MSC and Celebrity cruise lines of this world - navigating the seas with their trademark floating hotels.
The French, of course, do things differently. In Ponant's case, that means less is more. Less of the noise of the multitudes, but no shortage of on-tap champagne. Priorities, after all.
This cruise was pitched as 'Gentle Lands: Exploring Gardens and Historic Sites'. A bespoke odyssey aimed at those with green fingers or curious about Europe's glorious heritage, rather than someone who might like to round off the day with a rendition of My Way at the karaoke bar.
After slipping away from her moorings abreast the HMS Belfast, our ship transformed herself into a twinkling beacon of light and eased along the banks of the Thames. London, of course, twinkled right back.
Overnight, without us noticing, we docked discreetly at Ostend, and after a buffet breakfast, passengers set out on various excursions. I chose a short coach ride to Bruges, a city which seems to have re-invented itself as a living and breathing medieval museum. The trip included a stunning canal ride, and we marvelled at the sensitively restored and recreated architecture - but got the impression that it is all more pretty than real.
Again, we sailed effortlessly into the night before snaking up Belgium's Scheldt estuary. By daybreak, we had berthed in the heart of the captivating city of Antwerp, once home to Rubens and one of the great mercantile ports of medieval Europe.
For nine days and eight nights that was the pattern. Lots of leisure time on deck or lounging in comfy staterooms; the indolence interrupted occasionally by quick cultural smash-and-grabs onshore.
Your average bruiser cruiser will comfortably accommodate 3,000 passengers or more (Royal Caribbean's 'Symphony of the Seas', the biggest of these beasts on the seas, only runs out of bunks at 6,800 souls). Le Boréal, by contrast, welcomes a maximum of 264 passengers on six balconied decks, with half as many staff to cater for them.
It can't compete for variety and novelty, but Ponant makes a quiet fuss about offering quality instead. The ship features a la carte dining as well as a buffet restaurant. There is also the Le Club lounge for music and cabaret (unobtrusive and generally demure), a theatre for lectures (horticulturalists on this voyage), a small library and an internet lobby, though coverage was iffy, as can often be the case on cruises.
There is a small outdoor pool, but the chill coming in off the North Sea didn't encourage casual dippers. I did pedal furiously in the little fitness centre, however, and the spa next door was steadily booked.
There was always complimentary champagne in an ice bucket in Le Club, along with a range of wines and spirits. Cabin minibars, tantalisingly, were gratis too, testing the theory that you can't have too much of a good thing.
The cuisine is described as international, but it has a strong French bias, and while Ponant is particular about what you wear to dinner (no shorts, please), the atmosphere was far from starchy on our voyage.
Other than dinner, daily meals included continental and full breakfasts, buffet lunches and afternoon tea. The only reason to put your hand in your pocket was if you went man overboard with the drinks' menu.
I kept my feet dry. So, I suspect, did most of the other passengers - though I firmly got the impression that it wasn't because they couldn't afford to. They seemed to consist of either reserved and retired French couples, or Americans of a similar vintage. The cultural contrast between the two threw up some diverting moments.
It was the Americans who always wanted the chats, though. Returning to my cabin immediately after we had negotiated the Tower Bridge on that first night, a New Yorker (her twang unmistakable) shook me by the shoulders and yelled: "Wasn't that simply awesome?"
It sure was, lady.
Then, turning to her husband and wagging a finger in the vague direction of Le Club, she announced: "I sure could do with more of that bubbly."
And on she sailed.
Evenings on deck can shiver your timbers. Pack something warm and sensible. Comfy shoes are essential for city strolls (and cobblestones), and a posh frock or smart jacket are required for white-linen dining on board.
Ponant has two similar northern European cruises booking now.
'From the English Shores to Ireland', on Le Boréal, departs London on May 17, 2020, with prices from €2,570pp. Ports of call include London, Dover, Dartmouth, the Isles of Scilly, Glengarriff, Kinsale and Dublin.
'Treasures of the North Sea', on Le Bellot, departs Bergen on September 11, 2020 with stops including Amsterdam, Antwerp and Honfleur, from €3,340pp.
Frank was a guest of Ponant. Visit ponant.com, or call +33 4 88 66 64 00 to book.
From Frankfurt to Regensburg, by autobahn, takes four hours. The same journey by luxury U River Cruises, via the Main-Danube Canal and the Danube itself takes a leisurely seven days through stunningly scenic Bavaria. Way to go!