Waiting until you've retired to visit all your bucket-list destinations?
You might want to step on it.
With ice sheets melting, the Great Barrier Reef dying off and animals being poached to extinction on African savannahs, delaying your dream trips could be very costly.
That is what spurred Ms Valerie Jalufka into action.
"My advice is to get out there and see it, because the world is changing every year," says Ms Jalufka, a Houston IT consultant who at age 39 has already hit every continent on the planet.
Her most recent voyage was to Australia and New Zealand, where she spent three weeks bungee-jumping with the Kiwis and snorkeling at the Great Barrier Reef.
She has also gone on a safari in Tanzania, in Africa, and visited everywhere from Tasmania to Tierra del Fuego, often with the tour operator Abercrombie & Kent.
Ms Jalufka is part of a wave of youthful adventurers who are taking their once-in-a-lifetime trips in their 30s and 40s.
Their motivation is two-fold: An "experiences over stuff" mentality that is defining younger generations, and a "get there before it's gone" reality of a planet in the throes of climate change, making travel dreams more pressing than ever.
Of course, bucket lists themselves are not new.
About 54 per cent of travellers say they have travelled to cross something off their bucket list, and more than three-quarters of agencies say bucket-list travel will be "hot" or "very hot" this year.
But last year, a report for Berkshire Hathaway Travel Protection expected about a third of American travellers to Asia to be in their late 50s and early 60s.
Nope - turns out it was travellers in their 30s and 40s who headed there in droves.
"Younger travellers are thinking in terms of a bucket list, in much higher numbers than expected. It is kind of mind-blowing," said Mr Kit Kiefer, who authored the whitepaper for Berkshire Hathaway Travel Protection.
Among the locations being checked off by American travellers: Australia, with a 6.2 per cent increase expected this year, and Antarctica, which had a 10 per cent boost from Americans last year.
Perennial favourites like the pyramids in Egypt and African safaris are also luring bucket-listers abroad.
Tour providers are sniffing opportunity and are ramping up their offerings.
High-end vacation membership organisation Exclusive Resorts has 18 "Once-in-a-Lifetime" journeys, including diving with whale sharks off the Yucatan Peninsula and ice-trekking in Patagonia.
And you do not have to go totally broke to have unique experiences.
Some of the biggest year-over-year increases in travel have been places that have added more air routes or been aggressive in appealing to tourists with low-cost deals, like Reykjavik, in Iceland, Dubai or Portugal's Lisbon, said Mr Keith Nowak, communications director at booking website Travelocity.com.